A baseball bat strikes a baseball of mass that is at rest, and as a result the baseball files away from the bat. The kinetic energy gained by the baseball as it leaves the bat is due to the
(A) loss of mass after the ball is hit.
(B) gain in potential energy as the ball rises to the peak of its trajectory
(C) loss of potential energy of the ball as it falls back to the ground
(D) work done by the bat on the ball

(D) work done by the bat on the ball

Explanation:

The principle of work-energy theorem, states that work done by the sum of all the forces acting on an object, is equal to the gain in the kinetic energy of the object.

When the baseball bat strikes the baseball which causes a displacement in the initial position of the baseball, work is said to be done which is equal to the change in the kinetic energy of the baseball.

Thus, The kinetic energy gained by the baseball as it leaves the bat is due to the work done by the bat on the ball.