# Problem: A proton with an initial speed of 650,000 m/s is brought to rest by an electric field.1. What was the potential difference that stopped the proton?2. What was the initial kinetic energy of the proton, in electron volts?

###### FREE Expert Solution

Kinetic energy:

$\overline{)\begin{array}{rcl}\mathbf{K}\mathbf{.}\mathbf{E}& {\mathbf{=}}& \frac{\mathbf{1}}{\mathbf{2}}{\mathbf{mv}}^{\mathbf{2}}\end{array}}$

Potential energy:

$\overline{){\mathbf{U}}{\mathbf{=}}{\mathbf{q}}{\mathbf{V}}}$, where V is the potential, and q is the charge.

###### Problem Details

A proton with an initial speed of 650,000 m/s is brought to rest by an electric field.

1. What was the potential difference that stopped the proton?

2. What was the initial kinetic energy of the proton, in electron volts?