# Law of Universal Gravitation

#### ravennnn

3 10 kg spheres are located at the corners of a equilateral triangle of sides .5m. Calculate the magnitude of the total gravitational force exerted on one sphere by the other two.

I used G = 6.67 x 10^-11.

The answer I got was 4.62 x 10 ^-8. Can anyone confirm if this is correct, or explain how to get the correct answer?

#### fzero

Homework Helper
Gold Member
It's much better if you explain how you got that answer. This way any mistakes can be pointed out.

#### ravennnn

Well I picked the ball in the bottom left corner, and found that the vector components of the force the ball to the right of it exerts on it is (2.668 x 10^-8, 0).

The force the top ball exerts on the bottom left corner would have vector components (2.668 * 10^-8cos(60), 2.668 * 10^-8sin(60)). I added these two vectors up, and got the resultant vector components, which I used the distance formula to find the magnitude and got 4.62 x 10 ^-8.

#### ravennnn

Can anyone confirm if I did it right, or point out any mistakes I made?

#### fzero

Homework Helper
Gold Member
Looks good to me.

### The Physics Forums Way

We Value Quality
• Topics based on mainstream science
• Proper English grammar and spelling
We Value Civility
• Positive and compassionate attitudes
• Patience while debating
We Value Productivity
• Disciplined to remain on-topic
• Recognition of own weaknesses
• Solo and co-op problem solving