2 Charges Together, Resulting Speed After?

ghostbusters911

15th September 2011 - 08:06 AM

Two identical point charges, each with charge Q = 2.00 × 10-6 C and mass m = 9.0 × 10-3 g are released from rest when separated by d = 0.600 m. What is their speed when they are very far apart?

Attempt:
For the first part i used the equation: U=KQq/r - potential energy between two charges.
I found U to be .06 joules

U=K=1/2mv^2 cause it says very far away, and potential has turned all to kinetic energy. plugged in my mass and solved for v to be 115.47 m/s. but it appears to be wrong. any help plz?

rpenner

15th September 2011 - 08:16 AM

Hint: There are two masses.

ghostbusters911

15th September 2011 - 08:27 AM

thanks for replying so fast, i plugged in .000009kg(2) = .000018kg into K=1/2mv^2,

0.6=1/2(.000018)v^2

v came out to be 25.82m/s which is also wrong ..!

rpenner

15th September 2011 - 09:07 AM

I also get 0.06 J.

But I don't think you are doing the kinetic energy math correctly.

2 KE = 0.006 J which is off by an order of magnitude.

ghostbusters911

16th September 2011 - 03:46 AM

ty appreciate all the help

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