An object in circular motion has velocity that is constantly changing. the direction of the acceleration is

toward the center of the circle.
parallel to the motion, along the circle.
away from the center of the circle.

This situation is characteristic of the uniform circular motion , in which the movement of a body describes a circumference of a given radius with constant speed.  

However, in this movement the velocity has a constant magnitude, but its direction varies continuously.

Let's say is the velocity vector, whose direction is perpendicular to the radius of the trajectory, therefore   the acceleration is directed toward the center of the circumference.

choosing tennis and golf balls is your inde choice.

their mass and volume are dep

i think the answer would be reserve.