# Superposition of Gravitational Forces

1. Nov 13, 2012

### ieatplaydo

1. The problem statement, all variables and given/known data
a 7.0 kg point mass and a 17 kg point mass are held in place 0.5m apart. A particle of mass (m) is released from a point between the two masses 0.2m from the 7.0kg mass along the line connecting the two fixed masses. Find the magnitude and direction of the acceleration of the particle.

2. Relevant equations
F_g= (Gm_1 m_2)/r^2

3. The attempt at a solution
The force between the two distant masses: (G*7kg*17kg) / (0.5m)2
I know that these two distant masses exert an equal and opposite gravitational force on one another, but I don't know how to relate this force to the force exerted on the point mass in between them.

2. Nov 13, 2012

### Spinnor

You write,

"The force between the two distant masses: (G*7kg*17kg) / (0.5m)2
I know that these two distant masses exert an equal and opposite gravitational force on one another, but I don't know how to relate this force to the force exerted on the point mass in between them."

You need not be concerned with the force between the outer masses, we are told they are fixed in place so they don't move. You only want to know the forces on the central mass due to the 7 and 17Kg masses. Use the formula you listed.