Net Gravitational Force?

Question

I need to know the steps. I think I am doing it right, but I keep getting the answer wrong. Here's the question...

Objects with masses of 300 kg and a 600 kg are separated by 0.450 m.
(a) Find the net gravitational force exerted by these objects on a 69.0 kg object placed midway between them.

I am using the equation F=Gm1m2/d2, using it for the first object, then subtracting the second object and totally getting the wrong answer. Any help?

Answer 1

Since you're strugling, let's solve the problem

And let's cheat. The net gravitational force caused by two objects will be 300 kg in the direction of the bigger object.

F = G*m1*m2*d^-2
F= (6.67 × 10^−11 N m^2 kg^−2)(69kg)(300kg)(.225m^-2)
= 2.73 x 10^−5 N

You should get the same answer when you balance out the 600kg and 300kg objects. Make sure you are using the correct distance (.225m).

Good luck

Answer 2

Sounds like the right idea to me. Make sure you're keeping track of units and squaring the distances in the denominator like you're supposed to.

Answer 3

You are way too cute for your brain.