Question

Two plumbers are working at a site. The first tries to unscrew a pipe with a wrench and cannot budge it. The second one is twice as strong as the first one. He also has a wrench that is twice as long. How much more torque can the second plumber exert compared to the first?

Answer 1

Answer: The second plumber can exert 4 times more torque than the first one.

Explanation:

Torque is the cross product of force which causes rotation and the distance from the axis of rotation at which the force is applied.

τ = F × r

For the first plumber,

τ₁ = F₁ × r₁

For the second plumber,

τ₂ = F₂ × r₂ = 2 F₁ × 2 r₁ = 4 F₁ × r₁ = 4 τ₁  (∵ second plumber is twice as strong as first and second wrench is twice the length of first)

⇒τ₂ = 4 τ₁