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

Question

Quizplus · Accepted Answer

Once the force exerted on the fireman's hands equals the gravitational force, there is no net force acting on him. Therefore, he continues to descend at a constant speed, as there is no acceleration. This is known as terminal velocity, where the air resistance (in this case frictional force from the pole) balances out the gravitational force.

A Fireman Is Sliding Down a Fire Pole