How Much Charge Would the Moon and Earth Need to Replace Gravity?

[itzxmikee]

1. The Moon and Earth are bound together by gravity. If, instead, the force of attraction were the result of each having a charge of the same magnitude but opposite in sign, find the quantity of charge that would have to be placed on each to produce the required force.



2. Fe = ke |q1||q2|/r^2



3. 9.81 = ke |x||-x|/r^2
solving for x, I ended up getting -.64766

Not sure if I understand the problem correctly or not. Please help steer in the right direction. Thanks

 

[bel]

I think you need to equate the gravitational pull of the Earth on the moon with $$F_e$$. Since you know the radius from the center of the Earth to the center of the moon, and you know $$k_e$$, you can find the two "q"s by a simple square root operation, making one positive and the other negative.

 

[itzxmikee]

I got it..thanks