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 the force on his
Hands equals his weight, what happens to the fireman?
A) The fireman comes to a stop.
B) The fireman descends with a smaller but non-zero acceleration.
C) The fireman descends with slower and slower speed.
D) The acceleration of the fireman is now upward.
E) The fireman continues to descend, but with constant speed.

Question

Quizplus · Accepted Answer

When the vertical frictional force equals the fireman's weight, 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. Therefore, the fireman continues to move downward at a constant speed, not accelerating.

A Fireman Is Sliding Down a Fire Pole