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December 21, 2014

December 21, 2014

Posted by **Steve** on Friday, March 8, 2013 at 6:34pm.

If they are released at the same instant from rest, how fast will each be moving when they are very far away from each other? Assume they have identical masses of 2.0mg

- physics -
**bobpursley**, Friday, March 8, 2013 at 6:42pmHere is one way to do this.

I assume you are in calculus. Lets pretend we can do this charge by charge.

First charge:

work done=INT force dx from x=.03 to inf

where force=kq2q1/x^2

integrate it over that domain of x.

So that is the energy this partical has.

SEcond charge.

Now, with the first charge is gone, the second charge doesn't move.

So the total work in the system is what we figured on the first charge. So if both particles were released, this energy would have been divided evenly, so now we know the KE of each particle

KE=1/2 work done above

1/2 m v^2=1/2 work done above

solve for v

- physics -
**Steve**, Friday, March 8, 2013 at 6:45pmI am not in calculus. Is there any other way to to this through algebra?!

- physics -
**Damon**, Friday, March 8, 2013 at 6:53pmcalculate potential energy when close to each other.

You probably have the formula which Bob Pursley just told you how to derive with calculus by integrating the force

it is something like

U = k Q1 Q2 / R

The (1/2)m v^2 of each particle is half of that

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