Classical mechanics is the branch of physics used to describe the motion of macroscopic objects.^[1] It is the most familiar of the theories of physics. The concepts it covers, such as mass, acceleration, and force, are commonly used and known.^[2] The subject is based upon a three-dimensional Euclidean space with fixed axes, called a frame of reference. The point of concurrency of the three axes is known as the origin of the particular space.^[3]

Classical mechanics utilises many equations—as well as other mathematical concepts—which relate various physical quantities to one another. These include differential equations, manifolds, Lie groups, and ergodic theory.^[4] This article gives a summary of the most important of these.

This article lists equations from Newtonian mechanics, see analytical mechanics for the more general formulation of classical mechanics (which includes Lagrangian and Hamiltonian mechanics).

In the following rotational definitions, the angle can be any angle about the specified axis of rotation. It is customary to use θ, but this does not have to be the polar angle used in polar coordinate systems. The unit axial vector

$${\displaystyle \mathbf {\hat {n}} =\mathbf {\hat {e}} _{r}\times \mathbf {\hat {e}} _{\theta }}$$

defines the axis of rotation, ${\displaystyle \scriptstyle \mathbf {\hat {e}} _{r}}$ = unit vector in direction of r, ${\displaystyle \scriptstyle \mathbf {\hat {e}} _{\theta }}$ = unit vector tangential to the angle.

More information Translation, Rotation ...

	Translation	Rotation
Velocity	Average: $${\displaystyle \mathbf {v} _{\mathrm {average} }={\Delta \mathbf {r} \over \Delta t}}$$ Instantaneous: $${\displaystyle \mathbf {v} ={d\mathbf {r} \over dt}}$$	Angular velocity $${\displaystyle {\boldsymbol {\omega }}=\mathbf {\hat {n}} {\frac {{\rm {d}}\theta }{{\rm {d}}t}}}$$ Rotating rigid body: $${\displaystyle \mathbf {v} ={\boldsymbol {\omega }}\times \mathbf {r} }$$
Acceleration	Average: $${\displaystyle \mathbf {a} _{\mathrm {average} }={\frac {\Delta \mathbf {v} }{\Delta t}}}$$ Instantaneous: $${\displaystyle \mathbf {a} ={\frac {d\mathbf {v} }{dt}}={\frac {d^{2}\mathbf {r} }{dt^{2}}}}$$	Angular acceleration $${\displaystyle {\boldsymbol {\alpha }}={\frac {{\rm {d}}{\boldsymbol {\omega }}}{{\rm {d}}t}}=\mathbf {\hat {n}} {\frac {{\rm {d}}^{2}\theta }{{\rm {d}}t^{2}}}}$$ Rotating rigid body: $${\displaystyle \mathbf {a} ={\boldsymbol {\alpha }}\times \mathbf {r} +{\boldsymbol {\omega }}\times \mathbf {v} }$$
Jerk	Average: $${\displaystyle \mathbf {j} _{\mathrm {average} }={\frac {\Delta \mathbf {a} }{\Delta t}}}$$ Instantaneous: $${\displaystyle \mathbf {j} ={\frac {d\mathbf {a} }{dt}}={\frac {d^{2}\mathbf {v} }{dt^{2}}}={\frac {d^{3}\mathbf {r} }{dt^{3}}}}$$	Angular jerk $${\displaystyle {\boldsymbol {\zeta }}={\frac {{\rm {d}}{\boldsymbol {\alpha }}}{{\rm {d}}t}}=\mathbf {\hat {n}} {\frac {{\rm {d}}^{2}\omega }{{\rm {d}}t^{2}}}=\mathbf {\hat {n}} {\frac {{\rm {d}}^{3}\theta }{{\rm {d}}t^{3}}}}$$ Rotating rigid body: $${\displaystyle \mathbf {j} ={\boldsymbol {\zeta }}\times \mathbf {r} +{\boldsymbol {\alpha }}\times \mathbf {a} }$$

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The mechanical work done by an external agent on a system is equal to the change in kinetic energy of the system:

General work-energy theorem (translation and rotation)

The work done W by an external agent which exerts a force F (at r) and torque τ on an object along a curved path C is:

$${\displaystyle W=\Delta T=\int _{C}\left(\mathbf {F} \cdot \mathrm {d} \mathbf {r} +{\boldsymbol {\tau }}\cdot \mathbf {n} \,{\mathrm {d} \theta }\right)}$$

where θ is the angle of rotation about an axis defined by a unit vector n.

Kinetic energy

The change in kinetic energy for an object initially traveling at speed ${\displaystyle v_{0}}$ and later at speed ${\displaystyle v}$ is:

$${\displaystyle \Delta E_{k}=W={\frac {1}{2}}m(v^{2}-{v_{0}}^{2})}$$

Elastic potential energy

For a stretched spring fixed at one end obeying Hooke's law, the elastic potential energy is

$${\displaystyle \Delta E_{p}={\frac {1}{2}}k(r_{2}-r_{1})^{2}}$$

where r₂ and r₁ are collinear coordinates of the free end of the spring, in the direction of the extension/compression, and k is the spring constant.

Euler also worked out analogous laws of motion to those of Newton, see Euler's laws of motion. These extend the scope of Newton's laws to rigid bodies, but are essentially the same as above. A new equation Euler formulated is:^[10]

$${\displaystyle \mathbf {I} \cdot {\boldsymbol {\alpha }}+{\boldsymbol {\omega }}\times \left(\mathbf {I} \cdot {\boldsymbol {\omega }}\right)={\boldsymbol {\tau }}}$$

where I is the moment of inertia tensor.

The previous equations for planar motion can be used here: corollaries of momentum, angular momentum etc. can immediately follow by applying the above definitions. For any object moving in any path in a plane,

$${\displaystyle \mathbf {r} =\mathbf {r} (t)=r\mathbf {\hat {e}} _{r}}$$

the following general results apply to the particle.

More information Kinematics, Dynamics ...

Kinematics	Dynamics
Position $${\displaystyle \mathbf {r} =\mathbf {r} \left(r,\theta ,t\right)=r\mathbf {\hat {e}} _{r}}$$
Velocity $${\displaystyle \mathbf {v} =\mathbf {\hat {e}} _{r}{\frac {\mathrm {d} r}{\mathrm {d} t}}+r\omega \mathbf {\hat {e}} _{\theta }}$$	Momentum $${\displaystyle \mathbf {p} =m\left(\mathbf {\hat {e}} _{r}{\frac {\mathrm {d} r}{\mathrm {d} t}}+r\omega \mathbf {\hat {e}} _{\theta }\right)}$$ Angular momenta $${\displaystyle \mathbf {L} =m\mathbf {r} \times \left(\mathbf {\hat {e}} _{r}{\frac {\mathrm {d} r}{\mathrm {d} t}}+r\omega \mathbf {\hat {e}} _{\theta }\right)}$$
Acceleration $${\displaystyle \mathbf {a} =\left({\frac {\mathrm {d} ^{2}r}{\mathrm {d} t^{2}}}-r\omega ^{2}\right)\mathbf {\hat {e}} _{r}+\left(r\alpha +2\omega {\frac {\mathrm {d} r}{{\rm {d}}t}}\right)\mathbf {\hat {e}} _{\theta }}$$	The centripetal force is $${\displaystyle \mathbf {F} _{\bot }=-m\omega ^{2}R\mathbf {\hat {e}} _{r}=-\omega ^{2}\mathbf {m} }$$ where again m is the mass moment, and the Coriolis force is $${\displaystyle \mathbf {F} _{c}=2\omega m{\frac {{\rm {d}}r}{{\rm {d}}t}}\mathbf {\hat {e}} _{\theta }=2\omega mv\mathbf {\hat {e}} _{\theta }}$$ The Coriolis acceleration and force can also be written: $${\displaystyle \mathbf {F} _{c}=m\mathbf {a} _{c}=-2m{\boldsymbol {\omega \times v}}}$$

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Central force motion

For a massive body moving in a central potential due to another object, which depends only on the radial separation between the centers of masses of the two objects, the equation of motion is:

$${\displaystyle {\frac {d^{2}}{d\theta ^{2}}}\left({\frac {1}{\mathbf {r} }}\right)+{\frac {1}{\mathbf {r} }}=-{\frac {\mu \mathbf {r} ^{2}}{\mathbf {l} ^{2}}}\mathbf {F} (\mathbf {r} )}$$

These equations can be used only when acceleration is constant. If acceleration is not constant then the general calculus equations above must be used, found by integrating the definitions of position, velocity and acceleration (see above).

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Linear motion	Angular motion
${\displaystyle \mathbf {v-v_{0}} =\mathbf {a} t}$	${\displaystyle \omega -\omega _{0}=\alpha t}$
${\displaystyle \mathbf {x-x_{0}} ={\tfrac {1}{2}}(\mathbf {v_{0}+v} )t}$	${\displaystyle \theta -\theta _{0}={\tfrac {1}{2}}(\omega _{0}+\omega )t}$
${\displaystyle \mathbf {x-x_{0}} =\mathbf {v} _{0}t+{\tfrac {1}{2}}\mathbf {a} t^{2}}$	${\displaystyle \theta -\theta _{0}=\omega _{0}t+{\tfrac {1}{2}}\alpha t^{2}}$
${\displaystyle \mathbf {x} _{n^{th}}=\mathbf {v} _{0}+\mathbf {a} (n-{\tfrac {1}{2}})}$	${\displaystyle \theta _{n^{th}}=\omega _{0}+\alpha (n-{\tfrac {1}{2}})}$
${\displaystyle v^{2}-v_{0}^{2}=2\mathbf {a(x-x_{0})} }$	${\displaystyle \omega ^{2}-\omega _{0}^{2}=2\alpha (\theta -\theta _{0})}$

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For classical (Galileo-Newtonian) mechanics, the transformation law from one inertial or accelerating (including rotation) frame (reference frame traveling at constant velocity - including zero) to another is the Galilean transform.

Unprimed quantities refer to position, velocity and acceleration in one frame F; primed quantities refer to position, velocity and acceleration in another frame F' moving at translational velocity V or angular velocity Ω relative to F. Conversely F moves at velocity (—V or —Ω) relative to F'. The situation is similar for relative accelerations.

More information Motion of entities, Inertial frames ...

Motion of entities	Inertial frames	Accelerating frames
Translation V = Constant relative velocity between two inertial frames F and F'. A = (Variable) relative acceleration between two accelerating frames F and F'.	Relative position $${\displaystyle \mathbf {r} '=\mathbf {r} +\mathbf {V} t}$$ Relative velocity $${\displaystyle \mathbf {v} '=\mathbf {v} +\mathbf {V} }$$ Equivalent accelerations $${\displaystyle \mathbf {a} '=\mathbf {a} }$$	Relative accelerations $${\displaystyle \mathbf {a} '=\mathbf {a} +\mathbf {A} }$$ Apparent/fictitious forces $${\displaystyle \mathbf {F} '=\mathbf {F} -\mathbf {F} _{\mathrm {app} }}$$
Rotation Ω = Constant relative angular velocity between two frames F and F'. Λ = (Variable) relative angular acceleration between two accelerating frames F and F'.	Relative angular position $${\displaystyle \theta '=\theta +\Omega t}$$ Relative velocity $${\displaystyle {\boldsymbol {\omega }}'={\boldsymbol {\omega }}+{\boldsymbol {\Omega }}}$$ Equivalent accelerations $${\displaystyle {\boldsymbol {\alpha }}'={\boldsymbol {\alpha }}}$$	Relative accelerations $${\displaystyle {\boldsymbol {\alpha }}'={\boldsymbol {\alpha }}+{\boldsymbol {\Lambda }}}$$ Apparent/fictitious torques $${\displaystyle {\boldsymbol {\tau }}'={\boldsymbol {\tau }}-{\boldsymbol {\tau }}_{\mathrm {app} }}$$
	Transformation of any vector T to a rotating frame $${\displaystyle {\frac {{\rm {d}}\mathbf {T} '}{{\rm {d}}t}}={\frac {{\rm {d}}\mathbf {T} }{{\rm {d}}t}}-{\boldsymbol {\Omega }}\times \mathbf {T} }$$

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SHM, DHM, SHO, and DHO refer to simple harmonic motion, damped harmonic motion, simple harmonic oscillator and damped harmonic oscillator respectively.

More information Physical situation, Nomenclature ...

Equations of motion

Physical situation	Nomenclature	Translational equations	Angular equations
SHM	x = Transverse displacement θ = Angular displacement A = Transverse amplitude Θ = Angular amplitude	$${\displaystyle {\frac {\mathrm {d} ^{2}x}{\mathrm {d} t^{2}}}=-\omega ^{2}x}$$ Solution: $${\displaystyle x=A\sin \left(\omega t+\phi \right)}$$	$${\displaystyle {\frac {\mathrm {d} ^{2}\theta }{\mathrm {d} t^{2}}}=-\omega ^{2}\theta }$$ Solution: $${\displaystyle \theta =\Theta \sin \left(\omega t+\phi \right)}$$
Unforced DHM	b = damping constant κ = torsion constant	$${\displaystyle {\frac {\mathrm {d} ^{2}x}{\mathrm {d} t^{2}}}+b{\frac {\mathrm {d} x}{\mathrm {d} t}}+\omega ^{2}x=0}$$ Solution (see below for ω'): $${\displaystyle x=Ae^{-bt/2m}\cos \left(\omega '\right)}$$ Resonant frequency: $${\displaystyle \omega _{\mathrm {res} }={\sqrt {\omega ^{2}-\left({\frac {b}{4m}}\right)^{2}}}}$$ Damping rate: $${\displaystyle \gamma =b/m}$$ Expected lifetime of excitation: $${\displaystyle \tau =1/\gamma }$$	$${\displaystyle {\frac {\mathrm {d} ^{2}\theta }{\mathrm {d} t^{2}}}+b{\frac {\mathrm {d} \theta }{\mathrm {d} t}}+\omega ^{2}\theta =0}$$ Solution: $${\displaystyle \theta =\Theta e^{-\kappa t/2m}\cos \left(\omega \right)}$$ Resonant frequency: $${\displaystyle \omega _{\mathrm {res} }={\sqrt {\omega ^{2}-\left({\frac {\kappa }{4m}}\right)^{2}}}}$$ Damping rate: $${\displaystyle \gamma =\kappa /m}$$ Expected lifetime of excitation: $${\displaystyle \tau =1/\gamma }$$

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Angular frequencies

Physical situation	Nomenclature	Equations
Linear undamped unforced SHO	k = spring constant m = mass of oscillating bob	${\displaystyle \omega ={\sqrt {\frac {k}{m}}}}$
Linear unforced DHO	k = spring constant b = Damping coefficient	${\displaystyle \omega '={\sqrt {{\frac {k}{m}}-\left({\frac {b}{2m}}\right)^{2}}}}$
Low amplitude angular SHO	I = Moment of inertia about oscillating axis κ = torsion constant	${\displaystyle \omega ={\sqrt {\frac {\kappa }{I}}}}$
Low amplitude simple pendulum	L = Length of pendulum g = Gravitational acceleration Θ = Angular amplitude	Approximate value $${\displaystyle \omega ={\sqrt {\frac {g}{L}}}}$$ Exact value can be shown to be: $${\displaystyle \omega ={\sqrt {\frac {g}{L}}}\left[1+\sum _{k=1}^{\infty }{\frac {\prod _{n=1}^{k}\left(2n-1\right)}{\prod _{n=1}^{m}\left(2n\right)}}\sin ^{2n}\Theta \right]}$$

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Energy in mechanical oscillations

Physical situation	Nomenclature	Equations
SHM energy	T = kinetic energy U = potential energy E = total energy	Potential energy $${\displaystyle U={\frac {m}{2}}\left(x\right)^{2}={\frac {m\left(\omega A\right)^{2}}{2}}\cos ^{2}(\omega t+\phi )}$$ Maximum value at x = A: $${\displaystyle U_{\mathrm {max} }{\frac {m}{2}}\left(\omega A\right)^{2}}$$ Kinetic energy $${\displaystyle T={\frac {\omega ^{2}m}{2}}\left({\frac {\mathrm {d} x}{\mathrm {d} t}}\right)^{2}={\frac {m\left(\omega A\right)^{2}}{2}}\sin ^{2}\left(\omega t+\phi \right)}$$ Total energy $${\displaystyle E=T+U}$$
DHM energy		${\displaystyle E={\frac {m\left(\omega A\right)^{2}}{2}}e^{-bt/m}}$

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