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Net gravitational force

  • Thread starter phyhelpme
  • Start date
  • #1
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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.
 

Answers and Replies

  • #2
DaveC426913
Gold Member
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We don't spoonfeed homework here. Show your attempts.
 
  • #3
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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.
 
  • #4
DaveC426913
Gold Member
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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?
 
  • #5
10
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What value have you used for G?

9.8 m/s^2
 
  • #6
DaveC426913
Gold Member
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9.8 m/s^2
That's little g. You want http://en.wikipedia.org/wiki/Gravitational_constant" [Broken].
 
Last edited by a moderator:
  • #7
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Any advice on how I find it?
 
  • #8
10
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Your working the same problem?
 
  • #9
126
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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'. :smile:
 
  • #10
10
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The easiest way, I would think, would be to click on the link DaveC provided under 'big G'. :smile:
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?
 
Last edited:
  • #11
Redbelly98
Staff Emeritus
Science Advisor
Homework Helper
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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.
 

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