A rock weighing 20 n (mass = 2 kg) is swung in a horizontal circle of radius 2 m at a constant speed of 6 m/s. what is the centripetal acceleration of the rock?

Centripetal acceleration, same as the linear acceleration, is the rate of change of velocity but in this case the tangential velocity. The direction of this acceleration is always directed inward the motion. Centripetal acceleration is calculated from the ratio of the square of the velocity and the radius. We calculate as follows:

centripetal acceleration = v^2 / r

centripetal acceleration = (6 m/s) ^2 / 2 m

centripetal acceleration = 18 m/s^2