Answer:
When the cart gets to down-hill drop, for a moment it is at rest, until gravity (a force) acts upon the cart and causes it to accelerate downward.
Explanation:
Newton's second law says that when a constant force acts on a massive body, it causes it to accelerate, i.e., to change its velocity, at a constant rate. In the simplest case, a force applied to an object at rest causes it to accelerate in the direction of the force.
