# What is the gravitational force homework

1. Nov 12, 2008

### ganondorf29

1. The problem statement, all variables and given/known data

A solid sphere of uniform density has a mass of 3.0×10^4 kg and a radius of 1.0 m. What is the gravitational force due to the sphere on a particle of mass 1.0 kg located at a distance of 0.50 m from the center of the sphere?

2. Relevant equations

F = M1*M2*G / r^2

3. The attempt at a solution

F = (1*3E4*6.67E-11) / (0.5)^2

F = 8.00E-6 N

Am I doing something wrong because the question is asking for the force of a particle inside the sphere?

2. Nov 12, 2008

### borgwal

Re: Gravitation

Yes, the gravitational field inside a solid sphere is not simply proportional to 1/r^2.
Do you know Gauss' Law?

3. Nov 12, 2008

### LowlyPion

Re: Gravitation

The gravity inside a shell of uniform mass density will be 0.

So what you are interested in is how much mass remains in the sphere beneath you.

To calculate the effect of gravity at half the radius then you are only worried about the mass of attraction from a sphere of half the radius (since that's below the point of interest, with what is above having no effect).