Dynamics of circular motion

Dynamical criterion of circular motion

An object moves in uniform circular motion if and only if the net force vector has a radial component whose magnitude is equal to the centripetal force. If the net force also has a tangential component, the acceleration will have a tangential component and the motion will be non-uniform circular motion.

The net force vector acting on the object can be resolved into radial and tangential components:

\[\sum{\mathbf{F}} = \sum{\mathbf{F}_r} + \sum{\mathbf{F}_{\mathrm{t}}}.\]
In accordance with Newton's 2nd law, the radial component will be equal to the radial acceleration:

\[\left|\sum{\mathbf{F}_r}\right| = m \left|\mathbf{a}_r\right| = m \frac{v^2}{r} = m \omega^2 r.\]

The tangential component of the net force vector will cause tangential acceleration:
\[\sum{\mathbf{F}_{\mathrm{t}}} = m \mathbf{a}_{\mathrm{t}}.\]

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