A circular saw is powered by a motor. When the saw is used to cut wood, the wood exerts a torque of 0.80 N · m on the saw blade. If the blade rotates with a constant angular velocity of 20 rad/s the work done on the blade by the motor in 1.0 min is:
A) 0
B) 480 J
C) 960 J
D) 1400 J
E) 1800 J

Question

Quizplus · Accepted Answer

The work done by the motor is equal to the product of the torque and the angular displacement. Since the circular saw is rotating at a constant angular velocity, the angular displacement is given by:

Δθ = ωΔt = 20 rad/s x 60 s = 1200 rad

Therefore, the work done by the motor in 1.0 min is:

W = τΔθ = (0.80 N·m)(1200 rad) = 960 J

So the best choice is C.

A Circular Saw Is Powered by a Motor