A rock attached to a string swings in a vertical circle. Which free body diagram could correctly describe the force(s) on the rock when it is at the highest point?

Question

Quizplus · Accepted Answer

At the highest point, the tension force provided by the string acts as the centripetal force to maintain the circular motion of the rock. The weight of the rock acts downward and is balanced by the tension force from the string, resulting in a net force of zero in the vertical direction. This means that the normal force is also zero, and there is no force acting horizontally. Therefore, only the tension force and weight are present in the free body diagram at the highest point, as shown in choice C.

A Rock Attached to a String Swings in a Vertical