A fireman is sliding down a fire pole. As he speeds up, he tightens his grip on the pole, thus increasing the vertical frictional force that the pole exerts on the fireman. When this force equals the weight of the fireman, what happens?
A) The fireman comes to a stop.
B) The fireman descends with slower and slower speed.
C) The fireman descends with a smaller acceleration.
D) The fireman continues to descend, but with constant speed.
E) Cannot be determined without additional information.

Question

Quizplus · Accepted Answer

When the frictional force exerted by the pole equals the weight of the fireman, the net vertical force on the fireman becomes zero. Therefore, there is no further acceleration in the vertical direction. Since the fireman was already moving downwards, he will continue to move downwards with a constant speed. Hence, the correct option is (D).

A Fireman Is Sliding Down a Fire Pole