Problem 23.

A particle with a charge of +8 nC is in a uniform electric field E directed to the left. It is released from rest and moves to the left. After it has moved 3 cm, its kinetic energy is found to be

(a) What work was done by the electric force?

(b) What is the potential of the starting point with respect to the endpoint?

(c) What is the magnitude of E?

Solution

(a) The work done by electric force is exactly equal to the kinetic energy of the particle. So work is

(b) At the same time we can write the work done by electric force as the change of potential energy (or potential multiplied by the charge of the particle):

Then

(c) The potential difference is equal to E*d, where d is the traveled distance. Then