# Net Coloumb Force

1. Jul 25, 2011

### insanitey1

1. The problem statement, all variables and given/known data
Given the screen shots I am to calculate net force, Fc and direction, on the red object after 1.00 s

2. Relevant equations

3. The attempt at a solution
after doing using basic distance formula to calculate r I got a Force for the blue and red at 4.69x10^-3N and Force of the green and red at 9.04X10^-3N. I think i need to calculate Theta next but im not sure any help is much appreciated.

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2. Jul 26, 2011

### EWH

I would think you need a vector equation for force with time as the dependent variable. Is the second picture a given or is it your work? From the initial picture, all three charges should move (else why specify all three masses?), but the second picture only shows one charge moving.

If the 2nd pic is a given, then I'd figure the x and y distances for each, apply the inverse square law to each and add up the x and y forces separately, then combine the components using a rectangular to polar conversion to get an angle and a force.

Perhaps working in center of mass coordinates might be easier if all charges are actually moving away from each other rather than having 2 fixed.

3. Jul 26, 2011

### insanitey1

Yes the second one is a given. I was going to use basic trig and find the angle and that F+F and incorporate the angle does this sound right?