The ball shown in the figure will loop-the-loop if it starts from a point high enough on the incline.When the ball is at point A,the centripetal force on it is best represented by which of the following vectors?

Question

Quizplus · Accepted Answer

At point A, the ball is at the top of the incline and its potential energy is maximum while its kinetic energy is minimum. In order for the ball to successfully complete the loop-the-loop, it must have sufficient speed and the centripetal force must be greater than or equal to the gravitational force at every point along the loop.

At point A, the centripetal force on the ball is directed towards the center of the loop, and is equal to the sum of the gravitational force and the normal force (since the ball is in contact with the incline). The normal force N is perpendicular to the incline, while the gravitational force mg is directed downwards.

The correct representation of the forces acting on the ball at point A is shown in choice C, where the centripetal force is shown as the vector sum of the gravitational force mg and the normal force N, and is directed towards the center of the loop. This is the only choice where the net centripetal force is directed towards the center of the loop, as required for successful completion of the loop-the-loop.

The Ball Shown in the Figure Will Loop-The-Loop If It