Statics is the branch of classical mechanics that is concerned with the analysis of force and torque acting on a physical system that does not experience an acceleration , but rather is in equilibrium with its environment.
186-461: If F {\displaystyle {\textbf {F}}} is the total of the forces acting on the system, m {\displaystyle m} is the mass of the system and a {\displaystyle {\textbf {a}}} is the acceleration of the system, Newton's second law states that F = m a {\displaystyle {\textbf {F}}=m{\textbf {a}}\,} (the bold font indicates
372-432: A differential equation for S {\displaystyle S} . Bodies move over time in such a way that their trajectories are perpendicular to the surfaces of constant S {\displaystyle S} , analogously to how a light ray propagates in the direction perpendicular to its wavefront. This is simplest to express for the case of a single point mass, in which S {\displaystyle S}
558-466: A spiral . Archimedes' other mathematical achievements include deriving an approximation of pi ( π ) , defining and investigating the Archimedean spiral , and devising a system using exponentiation for expressing very large numbers . He was also one of the first to apply mathematics to physical phenomena , working on statics and hydrostatics . Archimedes' achievements in this area include
744-410: A vector quantity, i.e. one with both magnitude and direction ). If a = 0 {\displaystyle {\textbf {a}}=0} , then F = 0 {\displaystyle {\textbf {F}}=0} . As for a system in static equilibrium, the acceleration equals zero, the system is either at rest, or its center of mass moves at constant velocity . The application of
930-469: A 2-dimensional harmonic oscillator. However it is solved, the result is that orbits will be conic sections , that is, ellipses (including circles), parabolas , or hyperbolas . The eccentricity of the orbit, and thus the type of conic section, is determined by the energy and the angular momentum of the orbiting body. Planets do not have sufficient energy to escape the Sun, and so their orbits are ellipses, to
1116-470: A Circle . The actual value is approximately 1.7320508, making this a very accurate estimate. He introduced this result without offering any explanation of how he had obtained it. This aspect of the work of Archimedes caused John Wallis to remark that he was: "as it were of set purpose to have covered up the traces of his investigation as if he had grudged posterity the secret of his method of inquiry while he wished to extort from them assent to his results." It
1302-529: A Lagrangian for a multi-particle system, and so, Newton's third law is a theorem rather than an assumption. In Hamiltonian mechanics , the dynamics of a system are represented by a function called the Hamiltonian, which in many cases of interest is equal to the total energy of the system. The Hamiltonian is a function of the positions and the momenta of all the bodies making up the system, and it may also depend explicitly upon time. The time derivatives of
1488-441: A ball into a container after each mile traveled. As legend has it, Archimedes arranged mirrors as a parabolic reflector to burn ships attacking Syracuse using focused sunlight. While there is no extant contemporary evidence of this feat and modern scholars believe it did not happen, Archimedes may have written a work on mirrors entitled Catoptrica , and Lucian and Galen , writing in the second century AD, mentioned that during
1674-443: A body add as vectors , and so the total force on a body depends upon both the magnitudes and the directions of the individual forces. When the net force on a body is equal to zero, then by Newton's second law, the body does not accelerate, and it is said to be in mechanical equilibrium . A state of mechanical equilibrium is stable if, when the position of the body is changed slightly, the body remains near that equilibrium. Otherwise,
1860-411: A body moving in a circle of radius r {\displaystyle r} at a constant speed v {\displaystyle v} , its acceleration has a magnitude a = v 2 r {\displaystyle a={\frac {v^{2}}{r}}} and is directed toward the center of the circle. The force required to sustain this acceleration, called the centripetal force ,
2046-497: A circle. After four such steps, when the polygons had 96 sides each, he was able to determine that the value of π lay between 3 1 / 7 (approx. 3.1429) and 3 10 / 71 (approx. 3.1408), consistent with its actual value of approximately 3.1416. He also proved that the area of a circle was equal to π multiplied by the square of the radius of the circle ( π r 2 {\displaystyle \pi r^{2}} ). In On
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#17327868516702232-443: A constant speed in a straight line. This applies, for example, to a collision between two bodies. If the total external force is not zero, then the center of mass changes velocity as though it were a point body of mass M {\displaystyle M} . This follows from the fact that the internal forces within the collection, the forces that the objects exert upon each other, occur in balanced pairs by Newton's third law. In
2418-407: A force about any point is equal to the sum of the moments of the components of the force about the same point. The static equilibrium of a particle is an important concept in statics. A particle is in equilibrium only if the resultant of all forces acting on the particle is equal to zero. In a rectangular coordinate system the equilibrium equations can be represented by three scalar equations, where
2604-460: A function S ( q 1 , q 2 , … , t ) {\displaystyle S(\mathbf {q} _{1},\mathbf {q} _{2},\ldots ,t)} of positions q i {\displaystyle \mathbf {q} _{i}} and time t {\displaystyle t} . The Hamiltonian is incorporated into the Hamilton–Jacobi equation,
2790-484: A good approximation; because the planets pull on one another, actual orbits are not exactly conic sections. If a third mass is added, the Kepler problem becomes the three-body problem, which in general has no exact solution in closed form . That is, there is no way to start from the differential equations implied by Newton's laws and, after a finite sequence of standard mathematical operations, obtain equations that express
2976-408: A line which rotates with constant angular velocity . Equivalently, in modern polar coordinates ( r , θ ), it can be described by the equation r = a + b θ {\displaystyle \,r=a+b\theta } with real numbers a and b . This is an early example of a mechanical curve (a curve traced by a moving point ) considered by a Greek mathematician. This
3162-540: A magnetic field experiences a force that is also proportional to its charge, in a direction perpendicular to both the field and the body's direction of motion. Using the vector cross product , F = q E + q v × B . {\displaystyle \mathbf {F} =q\mathbf {E} +q\mathbf {v} \times \mathbf {B} .} Archimedes Archimedes of Syracuse ( / ˌ ɑːr k ɪ ˈ m iː d iː z / AR -kim- EE -deez ; c. 287 – c. 212 BC )
3348-410: A mechanics textbook that does not involve friction can be expressed in this way. The fact that the force can be written in this way can be understood from the conservation of energy . Without friction to dissipate a body's energy into heat, the body's energy will trade between potential and (non-thermal) kinetic forms while the total amount remains constant. Any gain of kinetic energy, which occurs when
3534-435: A mischaracterization. Archimedes was able to use indivisibles (a precursor to infinitesimals ) in a way that is similar to modern integral calculus . Through proof by contradiction ( reductio ad absurdum ), he could give answers to problems to an arbitrary degree of accuracy, while specifying the limits within which the answer lay. This technique is known as the method of exhaustion , and he employed it to approximate
3720-460: A number that was greater than the grains of sand needed to fill the universe. In doing so, he challenged the notion that the number of grains of sand was too large to be counted. He wrote: There are some, King Gelo , who think that the number of the sand is infinite in multitude; and I mean by the sand not only that which exists about Syracuse and the rest of Sicily but also that which is found in every region whether inhabited or uninhabited. To solve
3906-424: A person standing on the ground watching a train go past is an inertial observer. If the observer on the ground sees the train moving smoothly in a straight line at a constant speed, then a passenger sitting on the train will also be an inertial observer: the train passenger feels no motion. The principle expressed by Newton's first law is that there is no way to say which inertial observer is "really" moving and which
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#17327868516704092-740: A person, and focuses on the war machines that he is said to have built in order to defend the city from the Romans. Polybius remarks how, during the Second Punic War , Syracuse switched allegiances from Rome to Carthage , resulting in a military campaign under the command of Marcus Claudius Marcellus and Appius Claudius Pulcher , who besieged the city from 213 to 212 BC. He notes that the Romans underestimated Syracuse's defenses, and mentions several machines Archimedes designed, including improved catapults , crane-like machines that could be swung around in an arc, and other stone-throwers . Although
4278-484: A point mass is − ∂ S ∂ t = H ( q , ∇ S , t ) . {\displaystyle -{\frac {\partial S}{\partial t}}=H\left(\mathbf {q} ,\mathbf {\nabla } S,t\right).} The relation to Newton's laws can be seen by considering a point mass moving in a time-independent potential V ( q ) {\displaystyle V(\mathbf {q} )} , in which case
4464-446: A point, moving along some trajectory, and returning to the initial point — is zero. If this is the case, then the force can be written in terms of the gradient of a function called a scalar potential : F = − ∇ U . {\displaystyle \mathbf {F} =-\mathbf {\nabla } U\,.} This is true for many forces including that of gravity, but not for friction; indeed, almost any problem in
4650-411: A proof of the law of the lever , the widespread use of the concept of center of gravity , and the enunciation of the law of buoyancy known as Archimedes' principle . He is also credited with designing innovative machines , such as his screw pump , compound pulleys , and defensive war machines to protect his native Syracuse from invasion. Archimedes died during the siege of Syracuse , when he
4836-620: A reference to the mathematical drawing that he was supposedly studying when disturbed by the Roman soldier. There is no reliable evidence that Archimedes uttered these words and they do not appear in Plutarch's account. A similar quotation is found in the work of Valerius Maximus (fl. 30 AD), who wrote in Memorable Doings and Sayings , " ... sed protecto manibus puluere 'noli' inquit, 'obsecro, istum disturbare' " ("... but protecting
5022-405: A research program for physics, establishing that important goals of the subject are to identify the forces present in nature and to catalogue the constituents of matter. Overly brief paraphrases of the third law, like "action equals reaction " might have caused confusion among generations of students: the "action" and "reaction" apply to different bodies. For example, consider a book at rest on
5208-414: A single number, indicating where it is relative to some chosen reference point. For example, a body might be free to slide along a track that runs left to right, and so its location can be specified by its distance from a convenient zero point, or origin , with negative numbers indicating positions to the left and positive numbers indicating positions to the right. If the body's location as a function of time
5394-450: A situation, Newton's laws can be applied to the individual pieces of matter, keeping track of which pieces belong to the object of interest over time. For instance, if a rocket of mass M ( t ) {\displaystyle M(t)} , moving at velocity v ( t ) {\displaystyle \mathbf {v} (t)} , ejects matter at a velocity u {\displaystyle \mathbf {u} } relative to
5580-408: A solution that applied the hydrostatics principle known as Archimedes' principle , found in his treatise On Floating Bodies : a body immersed in a fluid experiences a buoyant force equal to the weight of the fluid it displaces. Using this principle, it would have been possible to compare the density of the crown to that of pure gold by balancing it on a scale with a pure gold reference sample of
5766-406: A stated sign convention, such as a plus sign (+) for counterclockwise moments and a minus sign (−) for clockwise moments, or vice versa. Moments can be added together as vectors. In vector format, the moment can be defined as the cross product between the radius vector, r (the vector from point O to the line of action), and the force vector, F : Varignon's theorem states that the moment of
Statics - Misplaced Pages Continue
5952-482: A system can lead to the whole system behaving in a radically different way within a short time. Noteworthy examples include the three-body problem, the double pendulum , dynamical billiards , and the Fermi–Pasta–Ulam–Tsingou problem . Newton's laws can be applied to fluids by considering a fluid as composed of infinitesimal pieces, each exerting forces upon neighboring pieces. The Euler momentum equation
6138-410: A system of two bodies with one much more massive than the other, the center of mass will approximately coincide with the location of the more massive body. When Newton's laws are applied to rotating extended bodies, they lead to new quantities that are analogous to those invoked in the original laws. The analogue of mass is the moment of inertia , the counterpart of momentum is angular momentum , and
6324-523: A table. The Earth's gravity pulls down upon the book. The "reaction" to that "action" is not the support force from the table holding up the book, but the gravitational pull of the book acting on the Earth. Newton's third law relates to a more fundamental principle, the conservation of momentum . The latter remains true even in cases where Newton's statement does not, for instance when force fields as well as material bodies carry momentum, and when momentum
6510-404: A temple dedicated to the goddess Aphrodite among its facilities. The account also mentions that, in order to remove any potential water leaking through the hull, a device with a revolving screw-shaped blade inside a cylinder was designed by Archimedes. Archimedes' screw was turned by hand, and could also be used to transfer water from a low-lying body of water into irrigation canals. The screw
6696-575: Is s ( t ) {\displaystyle s(t)} , then its average velocity over the time interval from t 0 {\displaystyle t_{0}} to t 1 {\displaystyle t_{1}} is Δ s Δ t = s ( t 1 ) − s ( t 0 ) t 1 − t 0 . {\displaystyle {\frac {\Delta s}{\Delta t}}={\frac {s(t_{1})-s(t_{0})}{t_{1}-t_{0}}}.} Here,
6882-412: Is looped to calculate, approximately, the bodies' trajectories. Generally speaking, the shorter the time interval, the more accurate the approximation. Newton's laws of motion allow the possibility of chaos . That is, qualitatively speaking, physical systems obeying Newton's laws can exhibit sensitive dependence upon their initial conditions: a slight change of the position or velocity of one part of
7068-418: Is "really" standing still. One observer's state of rest is another observer's state of uniform motion in a straight line, and no experiment can deem either point of view to be correct or incorrect. There is no absolute standard of rest. Newton himself believed that absolute space and time existed, but that the only measures of space or time accessible to experiment are relative. By "motion", Newton meant
7254-410: Is 4 π r for the sphere, and 6 π r for the cylinder (including its two bases), where r is the radius of the sphere and cylinder. This work of 28 propositions is also addressed to Dositheus. The treatise defines what is now called the Archimedean spiral . It is the locus of points corresponding to the locations over time of a point moving away from a fixed point with a constant speed along
7440-404: Is a force that varies randomly from instant to instant, representing the net effect of collisions with the surrounding particles. This is used to model Brownian motion . Newton's three laws can be applied to phenomena involving electricity and magnetism , though subtleties and caveats exist. Coulomb's law for the electric force between two stationary, electrically charged bodies has much
7626-520: Is a function S ( q , t ) {\displaystyle S(\mathbf {q} ,t)} , and the point mass moves in the direction along which S {\displaystyle S} changes most steeply. In other words, the momentum of the point mass is the gradient of S {\displaystyle S} : v = 1 m ∇ S . {\displaystyle \mathbf {v} ={\frac {1}{m}}\mathbf {\nabla } S.} The Hamilton–Jacobi equation for
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7812-435: Is a vector quantity, because its effect depends on the direction as well as on the magnitude of the action. Forces are classified as either contact or body forces. A contact force is produced by direct physical contact; an example is the force exerted on a body by a supporting surface. A body force is generated by virtue of the position of a body within a force field such as a gravitational, electric, or magnetic field and
7998-440: Is also referred to as torque . The magnitude of the moment of a force at a point O , is equal to the perpendicular distance from O to the line of action of F , multiplied by the magnitude of the force: M = F · d , where The direction of the moment is given by the right hand rule, where counter clockwise (CCW) is out of the page, and clockwise (CW) is into the page. The moment direction may be accounted for by using
8184-402: Is an expression of Newton's second law adapted to fluid dynamics. A fluid is described by a velocity field, i.e., a function v ( x , t ) {\displaystyle \mathbf {v} (\mathbf {x} ,t)} that assigns a velocity vector to each point in space and time. A small object being carried along by the fluid flow can change velocity for two reasons: first, because
8370-959: Is another re-expression of Newton's second law. The expression in brackets is a total or material derivative as mentioned above, in which the first term indicates how the function being differentiated changes over time at a fixed location, and the second term captures how a moving particle will see different values of that function as it travels from place to place: [ ∂ ∂ t + 1 m ( ∇ S ⋅ ∇ ) ] = [ ∂ ∂ t + v ⋅ ∇ ] = d d t . {\displaystyle \left[{\frac {\partial }{\partial t}}+{\frac {1}{m}}\left(\mathbf {\nabla } S\cdot \mathbf {\nabla } \right)\right]=\left[{\frac {\partial }{\partial t}}+\mathbf {v} \cdot \mathbf {\nabla } \right]={\frac {d}{dt}}.} In statistical physics ,
8556-417: Is based on the idea of specifying positions using numerical coordinates. Movement is represented by these numbers changing over time: a body's trajectory is represented by a function that assigns to each value of a time variable the values of all the position coordinates. The simplest case is one-dimensional, that is, when a body is constrained to move only along a straight line. Its position can then be given by
8742-466: Is constant. Alternatively, if p {\displaystyle \mathbf {p} } is known to be constant, it follows that the forces have equal magnitude and opposite direction. Various sources have proposed elevating other ideas used in classical mechanics to the status of Newton's laws. For example, in Newtonian mechanics, the total mass of a body made by bringing together two smaller bodies
8928-471: Is defined properly, in quantum mechanics as well. In Newtonian mechanics, if two bodies have momenta p 1 {\displaystyle \mathbf {p} _{1}} and p 2 {\displaystyle \mathbf {p} _{2}} respectively, then the total momentum of the pair is p = p 1 + p 2 {\displaystyle \mathbf {p} =\mathbf {p} _{1}+\mathbf {p} _{2}} , and
9114-413: Is equal in magnitude to the force that q 2 {\displaystyle q_{2}} exerts upon q 1 {\displaystyle q_{1}} , and it points in the exact opposite direction. Coulomb's law is thus consistent with Newton's third law. Electromagnetism treats forces as produced by fields acting upon charges. The Lorentz force law provides an expression for
9300-401: Is greater than zero the fluid will move in the direction of the resulting force. This concept was first formulated in a slightly extended form by French mathematician and philosopher Blaise Pascal in 1647 and became known as Pascal's Law . It has many important applications in hydraulics . Archimedes , Abū Rayhān al-Bīrūnī , Al-Khazini and Galileo Galilei were also major figures in
9486-444: Is independent of contact with any other body; an example of a body force is the weight of a body in the Earth's gravitational field. In addition to the tendency to move a body in the direction of its application, a force can also tend to rotate a body about an axis. The axis may be any line which neither intersects nor is parallel to the line of action of the force. This rotational tendency is known as moment of force ( M ). Moment
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#17327868516709672-608: Is its angle from the vertical. When the angle θ {\displaystyle \theta } is small, the sine of θ {\displaystyle \theta } is nearly equal to θ {\displaystyle \theta } (see Taylor series ), and so this expression simplifies to the equation for a simple harmonic oscillator with frequency ω = g / L {\displaystyle \omega ={\sqrt {g/L}}} . A harmonic oscillator can be damped, often by friction or viscous drag, in which case energy bleeds out of
9858-401: Is known as free fall . The speed attained during free fall is proportional to the elapsed time, and the distance traveled is proportional to the square of the elapsed time. Importantly, the acceleration is the same for all bodies, independently of their mass. This follows from combining Newton's second law of motion with his law of universal gravitation . The latter states that the magnitude of
10044-463: Is negligible. This is a reasonable approximation for real bodies when the motion of internal parts can be neglected, and when the separation between bodies is much larger than the size of each. For instance, the Earth and the Sun can both be approximated as pointlike when considering the orbit of the former around the latter, but the Earth is not pointlike when considering activities on its surface. The mathematical description of motion, or kinematics ,
10230-467: Is not the same as power or pressure , for example, and mass has a different meaning than weight . The physics concept of force makes quantitative the everyday idea of a push or a pull. Forces in Newtonian mechanics are often due to strings and ropes, friction, muscle effort, gravity, and so forth. Like displacement, velocity, and acceleration, force is a vector quantity. Translated from Latin, Newton's first law reads, Newton's first law expresses
10416-504: Is possible that he used an iterative procedure to calculate these values. In Quadrature of the Parabola , Archimedes proved that the area enclosed by a parabola and a straight line is 4 / 3 times the area of a corresponding inscribed triangle as shown in the figure at right. He expressed the solution to the problem as an infinite geometric series with the common ratio 1 / 4 : If
10602-473: Is some function of the position, V ( q ) {\displaystyle V(q)} . The physical path that the particle will take between an initial point q i {\displaystyle q_{i}} and a final point q f {\displaystyle q_{f}} is the path for which the integral of the Lagrangian is "stationary". That is, the physical path has
10788-639: Is sometimes presented as a definition of force, i.e., a force is that which exists when an inertial observer sees a body accelerating. In order for this to be more than a tautology — acceleration implies force, force implies acceleration — some other statement about force must also be made. For example, an equation detailing the force might be specified, like Newton's law of universal gravitation . By inserting such an expression for F {\displaystyle \mathbf {F} } into Newton's second law, an equation with predictive power can be written. Newton's second law has also been regarded as setting out
10974-532: Is still in use today for pumping liquids and granulated solids such as coal and grain. Described by Vitruvius , Archimedes' device may have been an improvement on a screw pump that was used to irrigate the Hanging Gardens of Babylon . The world's first seagoing steamship with a screw propeller was the SS Archimedes , which was launched in 1839 and named in honor of Archimedes and his work on
11160-401: Is the kinematic viscosity . It is mathematically possible for a collection of point masses, moving in accord with Newton's laws, to launch some of themselves away so forcefully that they fly off to infinity in a finite time. This unphysical behavior, known as a "noncollision singularity", depends upon the masses being pointlike and able to approach one another arbitrarily closely, as well as
11346-864: Is the density, P {\displaystyle P} is the pressure, and f {\displaystyle \mathbf {f} } stands for an external influence like a gravitational pull. Incorporating the effect of viscosity turns the Euler equation into a Navier–Stokes equation : ∂ v ∂ t + ( ∇ ⋅ v ) v = − 1 ρ ∇ P + ν ∇ 2 v + f , {\displaystyle {\frac {\partial v}{\partial t}}+(\mathbf {\nabla } \cdot \mathbf {v} )\mathbf {v} =-{\frac {1}{\rho }}\mathbf {\nabla } P+\nu \nabla ^{2}\mathbf {v} +\mathbf {f} ,} where ν {\displaystyle \nu }
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#173278685167011532-596: Is the distance from the center of the Earth to the body's location, which is very nearly the radius of the Earth. Setting this equal to m a {\displaystyle ma} , the body's mass m {\displaystyle m} cancels from both sides of the equation, leaving an acceleration that depends upon G {\displaystyle G} , M {\displaystyle M} , and r {\displaystyle r} , and r {\displaystyle r} can be taken to be constant. This particular value of acceleration
11718-424: Is the mass of the larger body being orbited. Therefore, the mass of a body can be calculated from observations of another body orbiting around it. Newton's cannonball is a thought experiment that interpolates between projectile motion and uniform circular motion. A cannonball that is lobbed weakly off the edge of a tall cliff will hit the ground in the same amount of time as if it were dropped from rest, because
11904-413: Is the sum of their individual masses. Frank Wilczek has suggested calling attention to this assumption by designating it "Newton's Zeroth Law". Another candidate for a "zeroth law" is the fact that at any instant, a body reacts to the forces applied to it at that instant. Likewise, the idea that forces add like vectors (or in other words obey the superposition principle ), and the idea that forces change
12090-563: Is therefore also directed toward the center of the circle and has magnitude m v 2 / r {\displaystyle mv^{2}/r} . Many orbits , such as that of the Moon around the Earth, can be approximated by uniform circular motion. In such cases, the centripetal force is gravity, and by Newton's law of universal gravitation has magnitude G M m / r 2 {\displaystyle GMm/r^{2}} , where M {\displaystyle M}
12276-499: Is to velocity as velocity is to position: it is the derivative of the velocity with respect to time. Acceleration can likewise be defined as a limit: a = d v d t = lim Δ t → 0 v ( t + Δ t ) − v ( t ) Δ t . {\displaystyle a={\frac {dv}{dt}}=\lim _{\Delta t\to 0}{\frac {v(t+\Delta t)-v(t)}{\Delta t}}.} Consequently,
12462-549: Is typically denoted g {\displaystyle g} : g = G M r 2 ≈ 9.8 m / s 2 . {\displaystyle g={\frac {GM}{r^{2}}}\approx \mathrm {9.8~m/s^{2}} .} If the body is not released from rest but instead launched upwards and/or horizontally with nonzero velocity, then free fall becomes projectile motion . When air resistance can be neglected, projectiles follow parabola -shaped trajectories, because gravity affects
12648-519: Is useful when calculating the motion of constrained bodies, like a mass restricted to move along a curving track or on the surface of a sphere. Hamiltonian mechanics is convenient for statistical physics , leads to further insight about symmetry, and can be developed into sophisticated techniques for perturbation theory . Due to the breadth of these topics, the discussion here will be confined to concise treatments of how they reformulate Newton's laws of motion. Lagrangian mechanics differs from
12834-415: The x {\displaystyle x} axis, and suppose an equilibrium point exists at the position x = 0 {\displaystyle x=0} . That is, at x = 0 {\displaystyle x=0} , the net force upon the body is the zero vector, and by Newton's second law, the body will not accelerate. If the force upon the body is proportional to the displacement from
13020-566: The Byzantine Greek architect Isidore of Miletus ( c. 530 AD ), while commentaries on the works of Archimedes written by Eutocius in the same century helped bring his work to a wider audience. Archimedes' work was translated into Arabic by Thābit ibn Qurra (836–901 AD), and into Latin via Arabic by Gerard of Cremona (c. 1114–1187). Direct Greek to Latin translations were later done by William of Moerbeke (c. 1215–1286) and Iacobus Cremonensis (c. 1400–1453). During
13206-595: The Renaissance and again in the 17th century , while the discovery in 1906 of previously lost works by Archimedes in the Archimedes Palimpsest has provided new insights into how he obtained mathematical results. Archimedes was born c. 287 BC in the seaport city of Syracuse , Sicily , at that time a self-governing colony in Magna Graecia . The date of birth is based on a statement by
13392-586: The Renaissance , the Editio princeps (First Edition) was published in Basel in 1544 by Johann Herwagen with the works of Archimedes in Greek and Latin. The following are ordered chronologically based on new terminological and historical criteria set by Knorr (1978) and Sato (1986). This is a short work consisting of three propositions. It is written in the form of a correspondence with Dositheus of Pelusium, who
13578-427: The heliocentric theory of the solar system proposed by Aristarchus of Samos , as well as contemporary ideas about the size of the Earth and the distance between various celestial bodies . By using a system of numbers based on powers of the myriad , Archimedes concludes that the number of grains of sand required to fill the universe is 8 × 10 in modern notation. The introductory letter states that Archimedes' father
13764-468: The kinetic theory of gases applies Newton's laws of motion to large numbers (typically on the order of the Avogadro number ) of particles. Kinetic theory can explain, for example, the pressure that a gas exerts upon the container holding it as the aggregate of many impacts of atoms, each imparting a tiny amount of momentum. The Langevin equation is a special case of Newton's second law, adapted for
13950-643: The lever , he gave a mathematical proof of the principle involved in his work On the Equilibrium of Planes . Earlier descriptions of the principle of the lever are found in a work by Euclid and in the Mechanical Problems , belonging to the Peripatetic school of the followers of Aristotle , the authorship of which has been attributed by some to Archytas . There are several, often conflicting, reports regarding Archimedes' feats using
14136-399: The partial derivatives of the Lagrangian gives d d t ( m q ˙ ) = − d V d q , {\displaystyle {\frac {d}{dt}}(m{\dot {q}})=-{\frac {dV}{dq}},} which is a restatement of Newton's second law. The left-hand side is the time derivative of the momentum, and the right-hand side is
14322-439: The siege of Syracuse Archimedes had burned enemy ships. Nearly four hundred years later, Anthemius , despite skepticism, tried to reconstruct Archimedes' hypothetical reflector geometry. The purported device, sometimes called " Archimedes' heat ray ", has been the subject of an ongoing debate about its credibility since the Renaissance . René Descartes rejected it as false, while modern researchers have attempted to recreate
14508-410: The "Newtonian" description (which itself, of course, incorporates contributions from others both before and after Newton). The physical content of these different formulations is the same as the Newtonian, but they provide different insights and facilitate different types of calculations. For example, Lagrangian mechanics helps make apparent the connection between symmetries and conservation laws, and it
14694-549: The Byzantine Greek scholar John Tzetzes that Archimedes lived for 75 years before his death in 212 BC. Plutarch wrote in his Parallel Lives that Archimedes was related to King Hiero II , the ruler of Syracuse, although Cicero suggests he was of humble origin. In the Sand-Reckoner , Archimedes gives his father's name as Phidias, an astronomer about whom nothing else is known. A biography of Archimedes
14880-478: The Earth" ( Greek : δῶς μοι πᾶ στῶ καὶ τὰν γᾶν κινάσω ). Olympiodorus later attributed the same boast to Archimedes' invention of the baroulkos , a kind of windlass , rather than the lever. A large part of Archimedes' work in engineering probably arose from fulfilling the needs of his home city of Syracuse . Athenaeus of Naucratis quotes a certain Moschion in a description on how King Hiero II commissioned
15066-470: The Earth, Sun, and Moon, as well as Aristarchus ' heliocentric model of the universe, in the Sand-Reckoner . Without the use of either trigonometry or a table of chords, Archimedes determines the Sun's apparent diameter by first describing the procedure and instrument used to make observations (a straight rod with pegs or grooves), applying correction factors to these measurements, and finally giving
15252-411: The Greek letter Δ {\displaystyle \Delta } ( delta ) is used, per tradition, to mean "change in". A positive average velocity means that the position coordinate s {\displaystyle s} increases over the interval in question, a negative average velocity indicates a net decrease over that interval, and an average velocity of zero means that the body ends
15438-820: The Hamilton–Jacobi equation becomes − ∂ S ∂ t = 1 2 m ( ∇ S ) 2 + V ( q ) . {\displaystyle -{\frac {\partial S}{\partial t}}={\frac {1}{2m}}\left(\mathbf {\nabla } S\right)^{2}+V(\mathbf {q} ).} Taking the gradient of both sides, this becomes − ∇ ∂ S ∂ t = 1 2 m ∇ ( ∇ S ) 2 + ∇ V . {\displaystyle -\mathbf {\nabla } {\frac {\partial S}{\partial t}}={\frac {1}{2m}}\mathbf {\nabla } \left(\mathbf {\nabla } S\right)^{2}+\mathbf {\nabla } V.} Interchanging
15624-434: The Newtonian formulation by considering entire trajectories at once rather than predicting a body's motion at a single instant. It is traditional in Lagrangian mechanics to denote position with q {\displaystyle q} and velocity with q ˙ {\displaystyle {\dot {q}}} . The simplest example is a massive point particle, the Lagrangian for which can be written as
15810-581: The Romans ultimately captured the city, they suffered considerable losses due to Archimedes' inventiveness. Cicero (106–43 BC) mentions Archimedes in some of his works. While serving as a quaestor in Sicily, Cicero found what was presumed to be Archimedes' tomb near the Agrigentine gate in Syracuse, in a neglected condition and overgrown with bushes. Cicero had the tomb cleaned up and was able to see
15996-528: The Sphere and Cylinder , Archimedes postulates that any magnitude when added to itself enough times will exceed any given magnitude. Today this is known as the Archimedean property of real numbers. Archimedes gives the value of the square root of 3 as lying between 265 / 153 (approximately 1.7320261) and 1351 / 780 (approximately 1.7320512) in Measurement of
16182-435: The acceleration is the second derivative of position, often written d 2 s d t 2 {\displaystyle {\frac {d^{2}s}{dt^{2}}}} . Position, when thought of as a displacement from an origin point, is a vector : a quantity with both magnitude and direction. Velocity and acceleration are vector quantities as well. The mathematical tools of vector algebra provide
16368-458: The angular mass, (SI units kg·m²) is a measure of an object's resistance to changes to its rotation. It is the inertia of a rotating body with respect to its rotation. The moment of inertia plays much the same role in rotational dynamics as mass does in linear dynamics, describing the relationship between angular momentum and angular velocity, torque and angular acceleration, and several other quantities. The symbols I and J are usually used to refer to
16554-412: The areas of figures and the value of π . In Measurement of a Circle , he did this by drawing a larger regular hexagon outside a circle then a smaller regular hexagon inside the circle, and progressively doubling the number of sides of each regular polygon , calculating the length of a side of each polygon at each step. As the number of sides increases, it becomes a more accurate approximation of
16740-406: The assumption of zero acceleration to the summation of moments acting on the system leads to M = I α = 0 {\displaystyle {\textbf {M}}=I\alpha =0} , where M {\displaystyle {\textbf {M}}} is the summation of all moments acting on the system, I {\displaystyle I} is the moment of inertia of
16926-535: The attracting force is proportional to the product of their masses, and inversely proportional to the square of the distance between them. Finding the shape of the orbits that an inverse-square force law will produce is known as the Kepler problem . The Kepler problem can be solved in multiple ways, including by demonstrating that the Laplace–Runge–Lenz vector is constant, or by applying a duality transformation to
17112-419: The basis for Newtonian mechanics , can be paraphrased as follows: The three laws of motion were first stated by Isaac Newton in his Philosophiæ Naturalis Principia Mathematica ( Mathematical Principles of Natural Philosophy ), originally published in 1687. Newton used them to investigate and explain the motion of many physical objects and systems. In the time since Newton, new insights, especially around
17298-661: The body's center of mass and movement around the center of mass. Significant aspects of the motion of an extended body can be understood by imagining the mass of that body concentrated to a single point, known as the center of mass. The location of a body's center of mass depends upon how that body's material is distributed. For a collection of pointlike objects with masses m 1 , … , m N {\displaystyle m_{1},\ldots ,m_{N}} at positions r 1 , … , r N {\displaystyle \mathbf {r} _{1},\ldots ,\mathbf {r} _{N}} ,
17484-744: The body's momentum, the Hamiltonian is H ( p , q ) = p 2 2 m + V ( q ) . {\displaystyle {\mathcal {H}}(p,q)={\frac {p^{2}}{2m}}+V(q).} In this example, Hamilton's equations are d q d t = ∂ H ∂ p {\displaystyle {\frac {dq}{dt}}={\frac {\partial {\mathcal {H}}}{\partial p}}} and d p d t = − ∂ H ∂ q . {\displaystyle {\frac {dp}{dt}}=-{\frac {\partial {\mathcal {H}}}{\partial q}}.} Evaluating these partial derivatives,
17670-435: The body's vertical motion and not its horizontal. At the peak of the projectile's trajectory, its vertical velocity is zero, but its acceleration is g {\displaystyle g} downwards, as it is at all times. Setting the wrong vector equal to zero is a common confusion among physics students. When a body is in uniform circular motion, the force on it changes the direction of its motion but not its speed. For
17856-410: The body. If the center of gravity coincides with the foundations, then the body is said to be metastable . Hydrostatics , also known as fluid statics , is the study of fluids at rest (i.e. in static equilibrium). The characteristic of any fluid at rest is that the force exerted on any particle of the fluid is the same at all points at the same depth (or altitude) within the fluid. If the net force
18042-416: The capture of Syracuse and Archimedes' role in it. Plutarch (45–119 AD) provides at least two accounts on how Archimedes died after Syracuse was taken. According to the most popular account, Archimedes was contemplating a mathematical diagram when the city was captured. A Roman soldier commanded him to come and meet Marcellus, but he declined, saying that he had to finish working on the problem. This enraged
18228-419: The capture of Syracuse in the Second Punic War , Marcellus is said to have taken back to Rome two mechanisms which were constructed by Archimedes and which showed the motion of the Sun, Moon and five planets. Cicero also mentions similar mechanisms designed by Thales of Miletus and Eudoxus of Cnidus . The dialogue says that Marcellus kept one of the devices as his only personal loot from Syracuse, and donated
18414-431: The carving and read some of the verses that had been added as an inscription. The tomb carried a sculpture illustrating Archimedes' favorite mathematical proof , that the volume and surface area of the sphere are two-thirds that of an enclosing cylinder including its bases. He also mentions that Marcellus brought to Rome two planetariums Archimedes built. The Roman historian Livy (59 BC–17 AD) retells Polybius's story of
18600-430: The case of describing a small object bombarded stochastically by even smaller ones. It can be written m a = − γ v + ξ {\displaystyle m\mathbf {a} =-\gamma \mathbf {v} +\mathbf {\xi } \,} where γ {\displaystyle \gamma } is a drag coefficient and ξ {\displaystyle \mathbf {\xi } }
18786-413: The center of mass is located at R = ∑ i = 1 N m i r i M , {\displaystyle \mathbf {R} =\sum _{i=1}^{N}{\frac {m_{i}\mathbf {r} _{i}}{M}},} where M {\displaystyle M} is the total mass of the collection. In the absence of a net external force, the center of mass moves at
18972-410: The concept of energy after Newton's time, but it has become an inseparable part of what is considered "Newtonian" physics. Energy can broadly be classified into kinetic , due to a body's motion, and potential , due to a body's position relative to others. Thermal energy , the energy carried by heat flow, is a type of kinetic energy not associated with the macroscopic motion of objects but instead with
19158-710: The concept of a limit . A function f ( t ) {\displaystyle f(t)} has a limit of L {\displaystyle L} at a given input value t 0 {\displaystyle t_{0}} if the difference between f {\displaystyle f} and L {\displaystyle L} can be made arbitrarily small by choosing an input sufficiently close to t 0 {\displaystyle t_{0}} . One writes, lim t → t 0 f ( t ) = L . {\displaystyle \lim _{t\to t_{0}}f(t)=L.} Instantaneous velocity can be defined as
19344-429: The concept of energy before that of force, essentially "introductory Hamiltonian mechanics". The Hamilton–Jacobi equation provides yet another formulation of classical mechanics, one which makes it mathematically analogous to wave optics . This formulation also uses Hamiltonian functions, but in a different way than the formulation described above. The paths taken by bodies or collections of bodies are deduced from
19530-414: The concept of energy, built the field of classical mechanics on his foundations. Limitations to Newton's laws have also been discovered; new theories are necessary when objects move at very high speeds ( special relativity ), are very massive ( general relativity ), or are very small ( quantum mechanics ). Newton's laws are often stated in terms of point or particle masses, that is, bodies whose volume
19716-410: The concept of the infinitely small and the method of exhaustion to derive and rigorously prove a range of geometrical theorems . These include the area of a circle , the surface area and volume of a sphere , the area of an ellipse , the area under a parabola , the volume of a segment of a paraboloid of revolution , the volume of a segment of a hyperboloid of revolution , and the area of
19902-503: The construction of these mechanisms entitled On Sphere-Making . Modern research in this area has been focused on the Antikythera mechanism , another device built c. 100 BC probably designed with a similar purpose. Constructing mechanisms of this kind would have required a sophisticated knowledge of differential gearing . This was once thought to have been beyond the range of the technology available in ancient times, but
20088-400: The contributions from each of the points. This provides a means to characterize a body's rotation about an axis, by adding up the angular momenta of its individual pieces. The result depends on the chosen axis, the shape of the body, and the rate of rotation. Newton's law of universal gravitation states that any body attracts any other body along the straight line connecting them. The size of
20274-558: The counterpart of force is torque . Angular momentum is calculated with respect to a reference point. If the displacement vector from a reference point to a body is r {\displaystyle \mathbf {r} } and the body has momentum p {\displaystyle \mathbf {p} } , then the body's angular momentum with respect to that point is, using the vector cross product , L = r × p . {\displaystyle \mathbf {L} =\mathbf {r} \times \mathbf {p} .} Taking
20460-441: The curvature of the Earth becomes significant: the ground itself will curve away from the falling cannonball. A very fast cannonball will fall away from the inertial straight-line trajectory at the same rate that the Earth curves away beneath it; in other words, it will be in orbit (imagining that it is not slowed by air resistance or obstacles). Consider a body of mass m {\displaystyle m} able to move along
20646-470: The density would be lower than that of gold. Archimedes found that this is what had happened, proving that silver had been mixed in. The story of the golden crown does not appear anywhere in Archimedes' known works. The practicality of the method described has been called into question due to the extreme accuracy that would be required to measure water displacement . Archimedes may have instead sought
20832-456: The design of a huge ship, the Syracusia , which could be used for luxury travel, carrying supplies, and as a display of naval power . The Syracusia is said to have been the largest ship built in classical antiquity and, according to Moschion's account, it was launched by Archimedes. The ship presumably was capable of carrying 600 people and included garden decorations, a gymnasium , and
21018-441: The development of hydrostatics. "Using a whole body of mathematical methods (not only those inherited from the antique theory of ratios and infinitesimal techniques, but also the methods of the contemporary algebra and fine calculation techniques), Arabic scientists raised statics to a new, higher level. The classical results of Archimedes in the theory of the centre of gravity were generalized and applied to three-dimensional bodies,
21204-616: The dialect of ancient Syracuse. Many written works by Archimedes have not survived or are only extant in heavily edited fragments; at least seven of his treatises are known to have existed due to references made by other authors. Pappus of Alexandria mentions On Sphere-Making and another work on polyhedra , while Theon of Alexandria quotes a remark about refraction from the now-lost Catoptrica . Archimedes made his work known through correspondence with mathematicians in Alexandria . The writings of Archimedes were first collected by
21390-404: The difference between its kinetic and potential energies: L ( q , q ˙ ) = T − V , {\displaystyle L(q,{\dot {q}})=T-V,} where the kinetic energy is T = 1 2 m q ˙ 2 {\displaystyle T={\frac {1}{2}}m{\dot {q}}^{2}} and the potential energy
21576-524: The discovery of the Antikythera mechanism in 1902 has confirmed that devices of this kind were known to the ancient Greeks. While he is often regarded as a designer of mechanical devices, Archimedes also made contributions to the field of mathematics . Plutarch wrote that Archimedes "placed his whole affection and ambition in those purer speculations where there can be no reference to the vulgar needs of life", though some scholars believe this may be
21762-426: The dust with his hands, said 'I beg of you, do not disturb this ' "). The most widely known anecdote about Archimedes tells of how he invented a method for determining the volume of an object with an irregular shape. According to Vitruvius , a crown for a temple had been made for King Hiero II of Syracuse , who supplied the pure gold to be used. The crown was likely made in the shape of a votive wreath . Archimedes
21948-609: The effect using only the means that would have been available to Archimedes, mostly with negative results. It has been suggested that a large array of highly polished bronze or copper shields acting as mirrors could have been employed to focus sunlight onto a ship, but the overall effect would have been blinding, dazzling , or distracting the crew of the ship rather than fire. Using modern materials and larger scale, sunlight-concentrating solar furnaces can reach very high temperatures, and are sometimes used for generating electricity . Archimedes discusses astronomical measurements of
22134-418: The energy of a body, have both been described as a "fourth law". The study of the behavior of massive bodies using Newton's laws is known as Newtonian mechanics. Some example problems in Newtonian mechanics are particularly noteworthy for conceptual or historical reasons. If a body falls from rest near the surface of the Earth, then in the absence of air resistance, it will accelerate at a constant rate. This
22320-423: The equilibrium is unstable. A common visual representation of forces acting in concert is the free body diagram , which schematically portrays a body of interest and the forces applied to it by outside influences. For example, a free body diagram of a block sitting upon an inclined plane can illustrate the combination of gravitational force, "normal" force , friction, and string tension. Newton's second law
22506-446: The equilibrium point, and directed to the equilibrium point, then the body will perform simple harmonic motion . Writing the force as F = − k x {\displaystyle F=-kx} , Newton's second law becomes m d 2 x d t 2 = − k x . {\displaystyle m{\frac {d^{2}x}{dt^{2}}}=-kx\,.} This differential equation has
22692-541: The feasibility of the claw, and in 2005 a television documentary entitled Superweapons of the Ancient World built a version of the claw and concluded that it was a workable device. Archimedes has also been credited with improving the power and accuracy of the catapult , and with inventing the odometer during the First Punic War . The odometer was described as a cart with a gear mechanism that dropped
22878-551: The first comprehensive compilation was not made until c. 530 AD by Isidore of Miletus in Byzantine Constantinople , while Eutocius ' commentaries on Archimedes' works in the same century opened them to wider readership for the first time. The relatively few copies of Archimedes' written work that survived through the Middle Ages were an influential source of ideas for scientists during
23064-519: The first term in this series is the area of the triangle, then the second is the sum of the areas of two triangles whose bases are the two smaller secant lines , and whose third vertex is where the line that is parallel to the parabola's axis and that passes through the midpoint of the base intersects the parabola, and so on. This proof uses a variation of the series 1/4 + 1/16 + 1/64 + 1/256 + · · · which sums to 1 / 3 . In The Sand Reckoner , Archimedes set out to calculate
23250-416: The first term is the total force upon the first body, and the second term is the total force upon the second body. If the two bodies are isolated from outside influences, the only force upon the first body can be that from the second, and vice versa. By Newton's third law, these forces have equal magnitude but opposite direction, so they cancel when added, and p {\displaystyle \mathbf {p} }
23436-670: The fluid density , and there is a net force upon it if the fluid pressure varies from one side of it to another. Accordingly, a = F / m {\displaystyle \mathbf {a} =\mathbf {F} /m} becomes ∂ v ∂ t + ( ∇ ⋅ v ) v = − 1 ρ ∇ P + f , {\displaystyle {\frac {\partial v}{\partial t}}+(\mathbf {\nabla } \cdot \mathbf {v} )\mathbf {v} =-{\frac {1}{\rho }}\mathbf {\nabla } P+\mathbf {f} ,} where ρ {\displaystyle \rho }
23622-415: The force of gravity only affects the cannonball's momentum in the downward direction, and its effect is not diminished by horizontal movement. If the cannonball is launched with a greater initial horizontal velocity, then it will travel farther before it hits the ground, but it will still hit the ground in the same amount of time. However, if the cannonball is launched with an even larger initial velocity, then
23808-459: The force upon a charged body that can be plugged into Newton's second law in order to calculate its acceleration. According to the Lorentz force law, a charged body in an electric field experiences a force in the direction of that field, a force proportional to its charge q {\displaystyle q} and to the strength of the electric field. In addition, a moving charged body in
23994-436: The force, represented in terms of the potential energy. Landau and Lifshitz argue that the Lagrangian formulation makes the conceptual content of classical mechanics more clear than starting with Newton's laws. Lagrangian mechanics provides a convenient framework in which to prove Noether's theorem , which relates symmetries and conservation laws. The conservation of momentum can be derived by applying Noether's theorem to
24180-498: The former equation becomes d q d t = p m , {\displaystyle {\frac {dq}{dt}}={\frac {p}{m}},} which reproduces the familiar statement that a body's momentum is the product of its mass and velocity. The time derivative of the momentum is d p d t = − d V d q , {\displaystyle {\frac {dp}{dt}}=-{\frac {dV}{dq}},} which, upon identifying
24366-426: The globe, it happened that the Moon followed the Sun by as many turns on that bronze contrivance as in the sky itself, from which also in the sky the Sun's globe became to have that same eclipse, and the Moon came then to that position which was its shadow on the Earth when the Sun was in line. This is a description of a small planetarium . Pappus of Alexandria reports on a now lost treatise by Archimedes dealing with
24552-444: The gravitational force from the Earth upon the body is F = G M m r 2 , {\displaystyle F={\frac {GMm}{r^{2}}},} where m {\displaystyle m} is the mass of the falling body, M {\displaystyle M} is the mass of the Earth, G {\displaystyle G} is Newton's constant, and r {\displaystyle r}
24738-455: The horizontal axis and 4 metres per second along the vertical axis. The same motion described in a different coordinate system will be represented by different numbers, and vector algebra can be used to translate between these alternatives. The study of mechanics is complicated by the fact that household words like energy are used with a technical meaning. Moreover, words which are synonymous in everyday speech are not so in physics: force
24924-424: The instantaneous velocity is the derivative of the position with respect to time. It can roughly be thought of as the ratio between an infinitesimally small change in position d s {\displaystyle ds} to the infinitesimally small time interval d t {\displaystyle dt} over which it occurs. More carefully, the velocity and all other derivatives can be defined using
25110-514: The lack of a relativistic speed limit in Newtonian physics. It is not yet known whether or not the Euler and Navier–Stokes equations exhibit the analogous behavior of initially smooth solutions "blowing up" in finite time. The question of existence and smoothness of Navier–Stokes solutions is one of the Millennium Prize Problems . Classical mechanics can be mathematically formulated in multiple different ways, other than
25296-416: The lever to lift very heavy objects. Plutarch describes how Archimedes designed block-and-tackle pulley systems, allowing sailors to use the principle of leverage to lift objects that would otherwise have been too heavy to move. According to Pappus of Alexandria , Archimedes' work on levers and his understanding of mechanical advantage caused him to remark: "Give me a place to stand on, and I will move
25482-408: The limit of the average velocity as the time interval shrinks to zero: d s d t = lim Δ t → 0 s ( t + Δ t ) − s ( t ) Δ t . {\displaystyle {\frac {ds}{dt}}=\lim _{\Delta t\to 0}{\frac {s(t+\Delta t)-s(t)}{\Delta t}}.} Acceleration
25668-416: The magnitude of the vector indicated by the length of the arrow. Numerically, a vector can be represented as a list; for example, a body's velocity vector might be v = ( 3 m / s , 4 m / s ) {\displaystyle \mathbf {v} =(\mathrm {3~m/s} ,\mathrm {4~m/s} )} , indicating that it is moving at 3 metres per second along
25854-699: The mass and α {\displaystyle \alpha } is the angular acceleration of the system. For a system where α = 0 {\displaystyle \alpha =0} , it is also true that M = 0. {\displaystyle {\textbf {M}}=0.} Together, the equations F = m a = 0 {\displaystyle {\textbf {F}}=m{\textbf {a}}=0} (the 'first condition for equilibrium') and M = I α = 0 {\displaystyle {\textbf {M}}=I\alpha =0} (the 'second condition for equilibrium') can be used to solve for unknown quantities acting on
26040-405: The means to describe motion in two, three or more dimensions. Vectors are often denoted with an arrow, as in s → {\displaystyle {\vec {s}}} , or in bold typeface, such as s {\displaystyle {\bf {s}}} . Often, vectors are represented visually as arrows, with the direction of the vector being the direction of the arrow, and
26226-445: The moment of inertia or polar moment of inertia. While a simple scalar treatment of the moment of inertia suffices for many situations, a more advanced tensor treatment allows the analysis of such complicated systems as spinning tops and gyroscopic motion. The concept was introduced by Leonhard Euler in his 1765 book Theoria motus corporum solidorum seu rigidorum ; he discussed the moment of inertia and many related concepts, such as
26412-409: The movements of the atoms and molecules of which they are made. According to the work-energy theorem , when a force acts upon a body while that body moves along the line of the force, the force does work upon the body, and the amount of work done is equal to the change in the body's kinetic energy. In many cases of interest, the net work done by a force when a body moves in a closed loop — starting at
26598-399: The negative derivative of the potential with the force, is just Newton's second law once again. As in the Lagrangian formulation, in Hamiltonian mechanics the conservation of momentum can be derived using Noether's theorem, making Newton's third law an idea that is deduced rather than assumed. Among the proposals to reform the standard introductory-physics curriculum is one that teaches
26784-425: The net force on the body accelerates it to a higher speed, must be accompanied by a loss of potential energy. So, the net force upon the body is determined by the manner in which the potential energy decreases. A rigid body is an object whose size is too large to neglect and which maintains the same shape over time. In Newtonian mechanics, the motion of a rigid body is often understood by separating it into movement of
26970-586: The order of the partial derivatives on the left-hand side, and using the power and chain rules on the first term on the right-hand side, − ∂ ∂ t ∇ S = 1 m ( ∇ S ⋅ ∇ ) ∇ S + ∇ V . {\displaystyle -{\frac {\partial }{\partial t}}\mathbf {\nabla } S={\frac {1}{m}}\left(\mathbf {\nabla } S\cdot \mathbf {\nabla } \right)\mathbf {\nabla } S+\mathbf {\nabla } V.} Gathering together
27156-412: The oscillator and the amplitude of the oscillations decreases over time. Also, a harmonic oscillator can be driven by an applied force, which can lead to the phenomenon of resonance . Newtonian physics treats matter as being neither created nor destroyed, though it may be rearranged. It can be the case that an object of interest gains or loses mass because matter is added to or removed from it. In such
27342-584: The other to the Temple of Virtue in Rome. Marcellus's mechanism was demonstrated, according to Cicero, by Gaius Sulpicius Gallus to Lucius Furius Philus , who described it thus: Hanc sphaeram Gallus cum moveret, fiebat ut soli luna totidem conversionibus in aere illo quot diebus in ipso caelo succederet, ex quo et in caelo sphaera solis fieret eadem illa defectio, et incideret luna tum in eam metam quae esset umbra terrae, cum sol e regione. When Gallus moved
27528-462: The pivot, the force upon the pendulum is gravity, and Newton's second law becomes d 2 θ d t 2 = − g L sin θ , {\displaystyle {\frac {d^{2}\theta }{dt^{2}}}=-{\frac {g}{L}}\sin \theta ,} where L {\displaystyle L} is the length of the pendulum and θ {\displaystyle \theta }
27714-400: The point relative to the foundations on which a body lies determines its stability in response to external forces. If the center of gravity exists outside the foundations, then the body is unstable because there is a torque acting: any small disturbance will cause the body to fall or topple. If the center of gravity exists within the foundations, the body is stable since no net torque acts on
27900-410: The position and momentum variables are given by partial derivatives of the Hamiltonian, via Hamilton's equations . The simplest example is a point mass m {\displaystyle m} constrained to move in a straight line, under the effect of a potential. Writing q {\displaystyle q} for the position coordinate and p {\displaystyle p} for
28086-502: The position and velocity the body has at a given time, like t = 0 {\displaystyle t=0} . One reason that the harmonic oscillator is a conceptually important example is that it is good approximation for many systems near a stable mechanical equilibrium. For example, a pendulum has a stable equilibrium in the vertical position: if motionless there, it will remain there, and if pushed slightly, it will swing back and forth. Neglecting air resistance and friction in
28272-413: The principal axis of inertia. Statics is used in the analysis of structures, for instance in architectural and structural engineering . Strength of materials is a related field of mechanics that relies heavily on the application of static equilibrium. A key concept is the center of gravity of a body at rest: it represents an imaginary point at which all the mass of a body resides. The position of
28458-416: The principle of inertia : the natural behavior of a body is to move in a straight line at constant speed. A body's motion preserves the status quo, but external forces can perturb this. The modern understanding of Newton's first law is that no inertial observer is privileged over any other. The concept of an inertial observer makes quantitative the everyday idea of feeling no effects of motion. For example,
28644-420: The principles derived to calculate the areas and centers of gravity of various geometric figures including triangles , parallelograms and parabolas . In this work of 24 propositions addressed to Dositheus, Archimedes proves by two methods that the area enclosed by a parabola and a straight line is 4/3 the area of a triangle with equal base and height. He achieves this in one of his proofs by calculating
28830-496: The problem, Archimedes devised a system of counting based on the myriad . The word itself derives from the Greek μυριάς , murias , for the number 10,000. He proposed a number system using powers of a myriad of myriads (100 million, i.e., 10,000 x 10,000) and concluded that the number of grains of sand required to fill the universe would be 8 vigintillion , or 8 × 10 . The works of Archimedes were written in Doric Greek ,
29016-712: The property that small perturbations of it will, to a first approximation, not change the integral of the Lagrangian. Calculus of variations provides the mathematical tools for finding this path. Applying the calculus of variations to the task of finding the path yields the Euler–Lagrange equation for the particle, d d t ( ∂ L ∂ q ˙ ) = ∂ L ∂ q . {\displaystyle {\frac {d}{dt}}\left({\frac {\partial L}{\partial {\dot {q}}}}\right)={\frac {\partial L}{\partial q}}.} Evaluating
29202-467: The quantity now called momentum , which depends upon the amount of matter contained in a body, the speed at which that body is moving, and the direction in which it is moving. In modern notation, the momentum of a body is the product of its mass and its velocity: p = m v , {\displaystyle \mathbf {p} =m\mathbf {v} \,,} where all three quantities can change over time. Newton's second law, in modern form, states that
29388-402: The rate of change of p {\displaystyle \mathbf {p} } is d p d t = d p 1 d t + d p 2 d t . {\displaystyle {\frac {d\mathbf {p} }{dt}}={\frac {d\mathbf {p} _{1}}{dt}}+{\frac {d\mathbf {p} _{2}}{dt}}.} By Newton's second law,
29574-399: The reference point ( r = 0 {\displaystyle \mathbf {r} =0} ) or if the force F {\displaystyle \mathbf {F} } and the displacement vector r {\displaystyle \mathbf {r} } are directed along the same line. The angular momentum of a collection of point masses, and thus of an extended body, is found by adding
29760-457: The result in the form of upper and lower bounds to account for observational error. Ptolemy , quoting Hipparchus, also references Archimedes' solstice observations in the Almagest . This would make Archimedes the first known Greek to have recorded multiple solstice dates and times in successive years. Cicero's De re publica portrays a fictional conversation taking place in 129 BC. After
29946-403: The rocket, then F = M d v d t − u d M d t {\displaystyle \mathbf {F} =M{\frac {d\mathbf {v} }{dt}}-\mathbf {u} {\frac {dM}{dt}}\,} where F {\displaystyle \mathbf {F} } is the net external force (e.g., a planet's gravitational pull). Physicists developed
30132-400: The same direction. The remaining term is the torque, τ = r × F . {\displaystyle \mathbf {\tau } =\mathbf {r} \times \mathbf {F} .} When the torque is zero, the angular momentum is constant, just as when the force is zero, the momentum is constant. The torque can vanish even when the force is non-zero, if the body is located at
30318-414: The same mathematical form as Newton's law of universal gravitation: the force is proportional to the product of the charges, inversely proportional to the square of the distance between them, and directed along the straight line between them. The Coulomb force that a charge q 1 {\displaystyle q_{1}} exerts upon a charge q 2 {\displaystyle q_{2}}
30504-453: The same weight, then immersing the apparatus in water. The difference in density between the two samples would cause the scale to tip accordingly. Galileo Galilei , who invented a hydrostatic balance in 1586 inspired by Archimedes' work, considered it "probable that this method is the same that Archimedes followed, since, besides being very accurate, it is based on demonstrations found by Archimedes himself." While Archimedes did not invent
30690-416: The screw. Archimedes is said to have designed a claw as a weapon to defend the city of Syracuse. Also known as " the ship shaker ", the claw consisted of a crane-like arm from which a large metal grappling hook was suspended. When the claw was dropped onto an attacking ship the arm would swing upwards, lifting the ship out of the water and possibly sinking it. There have been modern experiments to test
30876-559: The soldier, who killed Archimedes with his sword. Another story has Archimedes carrying mathematical instruments before being killed because a soldier thought they were valuable items. Marcellus was reportedly angered by Archimedes' death, as he considered him a valuable scientific asset (he called Archimedes "a geometrical Briareus ") and had ordered that he should not be harmed. The last words attributed to Archimedes are " Do not disturb my circles " ( Latin , " Noli turbare circulos meos "; Katharevousa Greek , "μὴ μου τοὺς κύκλους τάραττε"),
31062-532: The solution x ( t ) = A cos ω t + B sin ω t {\displaystyle x(t)=A\cos \omega t+B\sin \omega t\,} where the frequency ω {\displaystyle \omega } is equal to k / m {\displaystyle {\sqrt {k/m}}} , and the constants A {\displaystyle A} and B {\displaystyle B} can be calculated knowing, for example,
31248-450: The specific weight, which were based, in particular, on the theory of balances and weighing. The classical works of al-Biruni and al-Khazini may be considered the beginning of the application of experimental methods in medieval science ." Newton%27s second law Newton's laws of motion are three physical laws that describe the relationship between the motion of an object and the forces acting on it. These laws, which provide
31434-437: The sums of forces in all three directions are equal to zero. An engineering application of this concept is determining the tensions of up to three cables under load, for example the forces exerted on each cable of a hoist lifting an object or of guy wires restraining a hot air balloon to the ground. In classical mechanics, moment of inertia , also called mass moment, rotational inertia, polar moment of inertia of mass, or
31620-458: The system. Archimedes (c. 287–c. 212 BC) did pioneering work in statics. Later developments in the field of statics are found in works of Thebit . Force is the action of one body on another. A force is either a push or a pull, and it tends to move a body in the direction of its action. The action of a force is characterized by its magnitude, by the direction of its action, and by its point of application (or point of contact ). Thus, force
31806-510: The terms that depend upon the gradient of S {\displaystyle S} , [ ∂ ∂ t + 1 m ( ∇ S ⋅ ∇ ) ] ∇ S = − ∇ V . {\displaystyle \left[{\frac {\partial }{\partial t}}+{\frac {1}{m}}\left(\mathbf {\nabla } S\cdot \mathbf {\nabla } \right)\right]\mathbf {\nabla } S=-\mathbf {\nabla } V.} This
31992-528: The theory of ponderable lever was founded and the 'science of gravity' was created and later further developed in medieval Europe. The phenomena of statics were studied by using the dynamic approach so that two trends - statics and dynamics - turned out to be inter-related within a single science, mechanics. The combination of the dynamic approach with Archimedean hydrostatics gave birth to a direction in science which may be called medieval hydrodynamics. [...] Numerous experimental methods were developed for determining
32178-452: The three bodies' motions over time. Numerical methods can be applied to obtain useful, albeit approximate, results for the three-body problem. The positions and velocities of the bodies can be stored in variables within a computer's memory; Newton's laws are used to calculate how the velocities will change over a short interval of time, and knowing the velocities, the changes of position over that time interval can be computed. This process
32364-732: The time derivative of the angular momentum gives d L d t = ( d r d t ) × p + r × d p d t = v × m v + r × F . {\displaystyle {\frac {d\mathbf {L} }{dt}}=\left({\frac {d\mathbf {r} }{dt}}\right)\times \mathbf {p} +\mathbf {r} \times {\frac {d\mathbf {p} }{dt}}=\mathbf {v} \times m\mathbf {v} +\mathbf {r} \times \mathbf {F} .} The first term vanishes because v {\displaystyle \mathbf {v} } and m v {\displaystyle m\mathbf {v} } point in
32550-401: The time derivative of the momentum is the force: F = d p d t . {\displaystyle \mathbf {F} ={\frac {d\mathbf {p} }{dt}}\,.} If the mass m {\displaystyle m} does not change with time, then the derivative acts only upon the velocity, and so the force equals the product of the mass and the time derivative of
32736-546: The time interval in the same place as it began. Calculus gives the means to define an instantaneous velocity, a measure of a body's speed and direction of movement at a single moment of time, rather than over an interval. One notation for the instantaneous velocity is to replace Δ {\displaystyle \Delta } with the symbol d {\displaystyle d} , for example, v = d s d t . {\displaystyle v={\frac {ds}{dt}}.} This denotes that
32922-418: The value of a geometric series that sums to infinity with the ratio 1/4. In this two-volume treatise addressed to Dositheus, Archimedes obtains the result of which he was most proud, namely the relationship between a sphere and a circumscribed cylinder of the same height and diameter . The volume is 4 / 3 π r for the sphere, and 2 π r for the cylinder. The surface area
33108-444: The velocity field at its position is changing over time, and second, because it moves to a new location where the velocity field has a different value. Consequently, when Newton's second law is applied to an infinitesimal portion of fluid, the acceleration a {\displaystyle \mathbf {a} } has two terms, a combination known as a total or material derivative . The mass of an infinitesimal portion depends upon
33294-530: The velocity, which is the acceleration: F = m d v d t = m a . {\displaystyle \mathbf {F} =m{\frac {d\mathbf {v} }{dt}}=m\mathbf {a} \,.} As the acceleration is the second derivative of position with respect to time, this can also be written F = m d 2 s d t 2 . {\displaystyle \mathbf {F} =m{\frac {d^{2}\mathbf {s} }{dt^{2}}}.} The forces acting on
33480-411: Was a student of Conon of Samos . In Proposition II, Archimedes gives an approximation of the value of pi ( π ), showing that it is greater than 223 / 71 (3.1408...) and less than 22 / 7 (3.1428...). In this treatise, also known as Psammites , Archimedes finds a number that is greater than the grains of sand needed to fill the universe. This book mentions
33666-480: Was an Ancient Greek mathematician , physicist , engineer , astronomer , and inventor from the ancient city of Syracuse in Sicily . Although few details of his life are known, he is regarded as one of the leading scientists in classical antiquity . Regarded as the greatest mathematician of ancient history , and one of the greatest of all time, Archimedes anticipated modern calculus and analysis by applying
33852-494: Was an astronomer named Phidias. The Sand Reckoner is the only surviving work in which Archimedes discusses his views on astronomy. There are two books to On the Equilibrium of Planes : the first contains seven postulates and fifteen propositions , while the second book contains ten propositions. In the first book, Archimedes proves the law of the lever , which states that: Magnitudes are in equilibrium at distances reciprocally proportional to their weights. Archimedes uses
34038-417: Was asked to determine whether some silver had been substituted by the goldsmith without damaging the crown, so he could not melt it down into a regularly shaped body in order to calculate its density . In this account, Archimedes noticed while taking a bath that the level of the water in the tub rose as he got in, and realized that this effect could be used to determine the golden crown's volume . Archimedes
34224-412: Was killed by a Roman soldier despite orders that he should not be harmed. Cicero describes visiting Archimedes' tomb, which was surmounted by a sphere and a cylinder that Archimedes requested be placed there to represent his most valued mathematical discovery. Unlike his inventions, Archimedes' mathematical writings were little known in antiquity. Alexandrian mathematicians read and quoted him, but
34410-471: Was so excited by this discovery that he took to the streets naked, having forgotten to dress, crying " Eureka !" ( Greek : "εὕρηκα , heúrēka !, lit. ' I have found [it]! ' ). For practical purposes water is incompressible, so the submerged crown would displace an amount of water equal to its own volume. By dividing the mass of the crown by the volume of water displaced, its density could be obtained; if cheaper and less dense metals had been added,
34596-790: Was written by his friend Heracleides, but this work has been lost, leaving the details of his life obscure. It is unknown, for instance, whether he ever married or had children, or if he ever visited Alexandria , Egypt, during his youth. From his surviving written works, it is clear that he maintained collegial relations with scholars based there, including his friend Conon of Samos and the head librarian Eratosthenes of Cyrene . The standard versions of Archimedes' life were written long after his death by Greek and Roman historians. The earliest reference to Archimedes occurs in The Histories by Polybius ( c. 200–118 BC), written about 70 years after his death. It sheds little light on Archimedes as
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