Force between two charges is given by



Now in order to find the acceleration of each mass
we can use
F = ma

The magnitude of the resultant force is given by the centripetal force, since the car is under a circular motion. So, we have:

The centripetal acceleration is given by:

Where v is the linear speed and r the radius of the circular motion. Replacing this and solving:

Answer:
An outside force
Explanation:
Newton's law an object in motion stays in motion an object at rest stays at rest unless acted on by an outside force.