Notes on Centripetal Force
Newton’s first law states that an object in motion will continue its motion, in a straight line.
Therefore, if an object is moving in a circle, there must be a net force on the object to cause the
circular motion.
Centripetal force (Fc) is the NET force that keeps an object moving in a circle. It is directed
towards the center of the circle.
V
Fc
R
Centripetal acceleration (ac) = V2/R = 2R, where  is expressed in terms of radians
Net Force = mass x acceleration (Newton’s second law)
Therefore, centripetal force = mass x centripetal acceleration
Fc = mac = mV2 / R = m2R, where  is expressed in terms of radians
Fc = (Forces pointing towards the center) – (Forces pointing away from center)
Centripetal force is often set equal to another force, such as:
1.
2.
3.
4.
5.
Gravitational force
Electrostatic force
Tension
Friction
Normal Force