Question

A student holds one end of a string in a fixed position. A ball of mass 0.2 kg attached to the other end of the string moves in a horizontal circle of radius 0.5 m with a constant speed of 5 m/s. How much work is done on the ball by the string during each revolution?

Answer 1

Explanation:

Given that,

Mass of the ball, m = 0.2 kg

Radius of the circle, r = 0.5 m

Constant speed of the ball, v = 5 m/s

To find,

Work done on the ball.

Solve,

The given problem is the case of uniform circular motion. The velocity at each and every point is changing. The force acting on the object in uniform circular motion is called centripetal force. In the circular path, work done on the object is equal to zero as the force makes 90 degrees angle with the velocity and displacement.

$F=\dfrac{mv^2}{r}$

Since, F = 0

Work done, W = F.d

W = 0

Therefore, the work done on the ball by the string during each revolution is equal to zero.