Centripetal force is not a new type of force
Circular Motion - OCR A-Level Physics
$$\begin{aligned}
F &= \frac{mv^2}{r} \\
&= mr\omega^2
\end{aligned}$$
- Centripetal forceThe resultant force directed towards the centre of a circular path that causes an object to move in a circle. It is not a separate force but the net force providing circular motion. is not a new type of force. It is the resultant of real forces (gravity, tension, friction, normal contact) directed towards the centre.
- For a car on a flat road: friction provides the centripetal forceThe resultant force directed towards the centre of a circular path that causes an object to move in a circle. It is not a separate force but the net force providing circular motion..
- For a satellite in orbit: gravity provides the centripetal forceThe resultant force directed towards the centre of a circular path that causes an object to move in a circle. It is not a separate force but the net force providing circular motion..
- For a ball on a string (horizontal circle): the horizontal component of tension provides the centripetal forceThe resultant force directed towards the centre of a circular path that causes an object to move in a circle. It is not a separate force but the net force providing circular motion..
- If the centripetal force is removed, the object continues in a straight line tangent to the circle (Newton's first lawAn object remains at rest or moves with constant velocityThe rate of change of displacement. A vector quantity. Measured in m s⁻¹. unless acted on by a resultant force.).
Examiner Tips and Tricks
- Never write 'centripetal force' as a label on a free-body diagram.
- Instead label the real force (tension, friction, weight, normal reaction) and state that it provides the centripetal force.