More mass will in turn create more force in a collision.
The number of marbles in a collision will affect the outcome because they could bounce off each other and what not.
Answer:
The magnitude of the force is 1.29*10^-3N in the positive x direction
Explanation:
In order to calculate the magnitude and direction of the force, you take into account that the force is the space derivative of the potential enrgy, as follow:
(1)
where:

You replace the expression for U into the equation (1) and solve for F:
(2)
The force on the particle, for x = -0.080m is:

The magnitude of the force is 1.29*10^-3N in the positive x direction
I think it would be plum pudding, solid ball, solar system.