A mechanic needs 90 pound-feet of torque. Using a wrench 3 feet long, what force must be applied at the end?

Correct answer to question 100 (Mechanical Comprehension): 30 pounds

Method

Torque is force times the length of the moment arm, so the force is 90 / 3 = 30 pounds. Halving the wrench length would double the force needed, which is why a long breaker bar frees a stubborn nut.