Question

Suppose that a cart is moving along a road at a constant velocity. Give two examples of ways to cause the cart to decelerate, explaining how the net force is affected.(2 points)

Answer 1

1) Apply the brakes — braking increases the frictional force between wheels and road that points opposite the velocity. That introduces a nonzero net force backward, so by F = ma the cart acquires acceleration opposite its motion (it decelerates).

2) Drive the cart up an incline or uphill — the component of gravity along the slope points opposite the direction of motion. If this backward component exceeds any forward driving force (or the engine is cut), the net force is now backward and the cart decelerates.