physics question

Question

a fireman of mass 80 kg slides down a pole at constant speed. when he reaches the bottom, 4.2 m below his starting point, how much has thermal energy increased during his slide?

A. 2800 J

B. 3300 J

C. 1940 J

D. 980 J

Answer 1

Hi James,

There may be two possible reasons for a change in thermal energy, namely the change in kinetic energy or the change in potential (gravitational energy).

The fireman slides down a pole at a constant speed, so assuming that his mass did not change in the process, the kinetic energy did not change during his slide.

Now let us calculate the change in potential energy. It will be 80 kg x 4.2 m x 9.8 m s^-2 = 3,293 J ≈ 3,300 J

As the potential energy of the fireman decreased by 3,300 J, the thermal energy increased by the same amount.