Suppose you place a ball in the middle of a wagon, and then accelerate the wagon forward. Describe the motion of the ball relative to the ground. - Describe its motion relative to the wagon.

The motion of the ball relative to the ground is stationary

The motion of the ball relative to the wagon is backwards

Explanation:

To describe the motion of the ball relative to the ground, we note that

Assuming the ball is perfectly round and rotate freely, then we have

Force on the ball due to motion of the wagon = 0 N,

Then by the law of motion, an object will remain at rest when no force is applied to it

Therefore, apart from rotation of the ball, it will remain no displacement relative to the ground.

The motion of the ball relative to the wagon

Relative to the wagon, the ball appears to be moving in the opposite direction to the wagon, that is backwards.