Question

For a home repair job you must turn the handle of a screwdriver 24 times.

Part A If you apply an average force of 14 N tangentially to the 3.0-cm-diameter handle, how much work have you done?

Express your answer to two significant figures and include appropriate units.

Part B If you complete the job in 22 seconds, what was your average power output?

Express your answer to two significant figures and include appropriate units.

Answer 1

Work-done in rotational motion is given by:

W = *

= Torque applied by the average force = rxF = r*F*sin 90 deg

r = distance of force from the point where force is applied = 3.0 cm/2 = 1.50 cm = 0.0150 m

F = 14 N

= 0.0150*14*sin 90 deg

= angular displacement = 24 rev = 24*2*pi rad

So,

W = (0.0150*14*sin 90 deg)*24*2*pi

W = 31.67 J

In two significant figures

W = 32 J

Part B.

Power = Work-done/time taken

P = W/t = 31.67/22

Pavg = 1.4395 W = Average power output

In two significant figures

P_avg = 1.4 W

Please Upvote.