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, which of the following happens?
A)The fireman comes to a stop.
B)The fireman descends at slower and slower speed.
C)The fireman descends with a smaller acceleration.
D)The fireman continues to descend, but at a constant speed.

Question

Quizplus · Accepted Answer

When the vertical frictional force equals the weight of the fireman, the net force acting on the fireman becomes zero. According to Newton's second law, when the net force is zero, the acceleration is also zero, meaning the fireman will continue moving at whatever speed he has at that moment, which is a constant speed.

A Fireman Is Sliding Down a Fire Pole