Question

A small ball is tied to a string and set rotating with negligible friction in a vertical circle. If the ball moves over the top of the circle at its slowest possible speed (so that the tension in the string is negligible), what is the tension in the string at the bottom of the circle, assuming there is no additional energy added to the ball during rotation?

a) Equal to the weight of the ball
b) Less than the weight of the ball
c) Greater than the weight of the ball
d) Zero

Answer 1

The tension in the string at the bottom of the circle, when the ball is moving at its slowest possible speed, is equal to the weight of the ball.

Step-by-step explanation:

When the ball moves over the top of the circle at its slowest possible speed, the tension in the string is negligible. This means that the tension in the string at the bottom of the circle will be equal to the weight of the ball. This is because the tension in the string provides the centripetal force needed to keep the ball moving in a circular path. At the top of the circle, the tension in the string is equal to the weight of the ball plus the centripetal force due to its speed. So, at the bottom of the circle where the ball is moving the slowest, the tension in the string is equal to the weight of the ball.