# Electrostatic Potential Energy

## Homework Statement

As an electron moved through a region of space, its speed changed from an initial velocity of vi=8114.3 km/s to the final velocity vf=2233.7 km/s. The electric force was the only force acting on the electron.

Across what potential difference did the electron travel?

## Homework Equations

Qe * V = (0.5 * m * Vf^2) - (0.5 * m * Vi^2)

Qe = Charge of Electron = -1.602 * 10^(-19)
V = Potential Difference
m = Mass of Electron

## The Attempt at a Solution

V = [( 0.5 ) * ( 9.11*10^-31 kg ) * ( 2.2337*10^6 m/s )^2] - [( 0.5 ) * ( 9.11*10^-31 kg ) * ( 8.1143*10^6 m/s )^2] /
( -1.602*10^-19 C )

The answer I keep getting is V = 173 Volts, but that's incorrect. It may be my math, but if anyone can help I would appreciate it.

## Answers and Replies

TSny
Homework Helper
Gold Member
I think you are close to the right answer. If an electron goes from a point of lower potential to a point of higher potential would the electron slow down or speed up?