Assume that 10 J of work is needed to push a charge, at rest, into an electric field. After the charge is released there, it flies back to its starting position and its kinetic energy there will be
A) 5 J.
B) zero.
C) 10 J.
D) more than 10 J.
E) impossible to predict without additional information.

Question

Quizplus · Accepted Answer

The principle of conservation of energy states that energy cannot be created or destroyed, only transformed from one form to another. In this case, the 10 J of work done to push the charge into the electric field is converted into potential energy. When the charge is released and returns to its starting position, this potential energy is converted back into kinetic energy. Therefore, the kinetic energy of the charge at its starting position will be 10 J, the same amount of energy that was initially put in to move it.

Assume That 10 J of Work Is Needed to Push