Final answer:
A stop and then a reversal of direction results in a greater change in momentum than just stopping. This occurs because the total change in velocity is greater due to the object first coming to a stop and then accelerating in the opposite direction, doubling the change in momentum.
Step-by-step explanation:
The greater change in momentum occurs when an object stops and then reverses direction, compared to just stopping. Momentum is defined as the product of a body’s mass and its velocity. A change in momentum (ΔP) is equivalent to the mass times the change in velocity (Δv). When an object stops, its velocity changes from an initial value to zero. However, when it reverses direction, it has to first come to a stop and then gain velocity in the opposite direction. This means the total change in velocity is greater when an object reverses direction as it undergoes a change in velocity twice: first slowing down to zero, then accelerating in the opposite direction.
For example, if a car traveling north at a certain velocity comes to a stop, its change in velocity is equal to the negative of its initial velocity. If the same car then reverses and starts traveling south at the same speed, its final velocity is equal to its initial velocity, but in the opposite direction, which gives a change in velocity that is twice the magnitude of the car's initial velocity. Consequently, the change in momentum for the stop and reversal is twice that of merely coming to a stop.