A proton in a uniform electric field of 3.0 X 105 N/C is moving with an initial speed of 800,000 m/s in the direction direction opposite the direction of the field. After traveling a distance d, It is brought to rest (for an instant) before moving in the reverse direction.
a) What was the proton's initial kinetic energy?
b) What was the change in the proton's potential energy over the distance d?
c) Through what potential difference did it move before coming to rest?
d) How far did it travel before coming to rest?