Calculating Net Gravitational Force Between Multiple Objects

[phyhelpme]

Confused :(

Homework Statement

A 200 kg object and a 500 kg object are separated by 0.500 m. Find the net gravitational force exerted by these objects on a 50.0 kg object placed midway between them.

 

[DaveC426913]

We don't spoonfeed homework here. Show your attempts.

 

[phyhelpme]

I have:
F= Gm1m2/r^2
F= G(50.0kg)(500kg-200kg)/0.25m^2 =240000N toward 500kg

I feel that I have it setup right but for some reason when I calculate I get 2400000 which seems wrong to me.

 

[DaveC426913]

I have:
F= Gm1m2/r^2
F= G(50.0kg)(500kg-200kg)/0.25m^2 =240000N toward 500kg

I feel that I have it setup right but for some reason when I calculate I get 2400000 which seems wrong to me.

What value have you used for G?

 

[phyhelpme]

What value have you used for G?

9.8 m/s^2

 

[DaveC426913]

9.8 m/s^2

That's little g. You want http://en.wikipedia.org/wiki/Gravitational_constant" .

 

[qwerty11]

Any advice on how I find it?

 

[phyhelpme]

Your working the same problem?

 

[dotman]

Any advice on how I find it?

The easiest way, I would think, would be to click on the link DaveC provided under 'big G'.

 

[phyhelpme]

The easiest way, I would think, would be to click on the link DaveC provided under 'big G'.

If it was a snake it would have bitten me.

So G is 6.674 x 10^-11N (m/kg)^2 correct?

That would mean my equation is:
F= 6.674 x 10^-11(50.0kg)(500kg-200kg)/0.25m^2 =1.60176 x 10^-5N toward 500kg?

 

[Redbelly98]

No, you don't subtract the masses.

Calculate the forces separately, between the 200&50 kg masses, and then between the 500&50 kg masses. Then use vector addidtion to add these two forces together. Important: add the forces as vectors, don't just add the two numbers together.