Electric Fields and Final Velocity of point particle question? Electric Fields and F

longcatislong

1. The problem statement, all variables and given/known data

A fixed charge Q= +3.65 µC is held fixed at the origin of an xy plane. A second charge q= +5.11 µC is released from rest at the xy coordinate of (+1.15 m, +0.810 m).

a) (a) If the mass of q is 2.90 g, what is its speed when it moves infinitely far from the origin?

(b) At what distance from the origin does q attain half the speed it will have at infinity*?
(*Please note where most of the energy exchange occurs!)

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2. Relevant equations

Ei=Ef
KQq/r=Fe=qV
1/2mv^2


3. The attempt at a solution

I solved for a) and got 9.07202 m/s
Can't seem to figure out way to do b. Initially I just took 1/2 the velocity I got in a), plugged it into the equation KQq/r=1/2mv^2 to solve for a n R, but that's wrong. Any help is appreciated.

Spinnor

What did you get?