A stone is tied to a string and rotated in a circular path. The pull of our hand on the string is towards the centre of the circular path traced by the stone. The tension in the string provides the centripetal force. If the string is suddenly released, the stone will go off in a direction tangential to the circle.

1. Centripetal force
A stone is tied to a string and rotated in a circular path. The pull
of our hand on the string is towards the centre of the circular
path traced by the stone. The tension in the string provides the
centripetal force. If the string is suddenly released, the stone will
go off in a direction tangential to the circle.

2. When a satellite moves in a circular path around the earth, the
gravitational force between the earth and the satellite provides the
necessary centripetal force. For a car taking a curve, the frictional
force on the tyres and the ground provides the required centripetal
force.
The external force required to make a body move along a
circular path with uniform speed and directed towards the
centre is called centripetal force.

3. Let us consider an object of mass ‘m’, moving along a circular
path of radius ‘r’ with an angular velocity  and linear velocity ‘v’.
As the body moves along the circular path, the direction of
velocity changes at every point and hence it has an acceleration,
which is directed towards the centre. This acceleration is called
centripetal acceleration.

4. Centripetal acceleration a =
Centripetal force F = mass × acceleration
= m x =
Centripetal force F = m r 2 ( v = r)

v2
r
v2
r
mv2
r