How far does the particle travel?

[hichangkyu]

Homework Statement

A charge of -1.8 µC is fixed in place. From a horizontal distance of 0.0450 m, a particle of mass 2.25 10-3 kg and charge -1.7 µC is fired with an initial speed of 65.0 m/s directly toward the fixed charge. How far does the particle travel before its speed is zero?

Homework Equations

q(V) = 1/2mv^2 (??)

The Attempt at a Solution

I'm afraid I'm very lost on this one. I messed around with the equation for collisions a bit but I can't seem to get in the right direction much less get the answer.

I would be grateful if you guys could provide me with some hints to get started >.<
thanks!

 

[tiny-tim]

Welcome to PF!

A charge of -1.8 µC is fixed in place. From a horizontal distance of 0.0450 m, a particle of mass 2.25 10-3 kg and charge -1.7 µC is fired with an initial speed of 65.0 m/s directly toward the fixed charge. How far does the particle travel before its speed is zero?

Hi hichangkyu! Welcome to PF!

Hint: just use KE + PE = constant.

 

[nckaytee]

I am having the same problem. I do not get KE + PE = constant?!

 

[tiny-tim]

I am having the same problem. I do not get KE + PE = constant?!

Hi nckaytee!

KE = 1/2 mv², and PE = … ?