A 1.5m long dowel is pivoted about the end so that it is a pendulum of sorts - it can freely swing in a vertical plane. At the other end of the dowel is a brass weight having mass 1.5 kg. (The center of the brass weight is 1.5 m from the pivot point. When the rod is positioned in its swing such that its angle with the vertical is 22.5 degrees, what is the torque on the rod about the pivot due to the presence of the brass weight?
A) 8.4 N·m
B) 22 N·m
C) 20 N·m
D) 9.1 N·m

Question

Quizplus · Accepted Answer

The torque τ is given by τ = r * F * sin(θ), where r = 1.5 m, F = mg = 1.5 kg * 9.8 m/s² = 14.7 N, and θ = 22.5 degrees. Thus, τ = 1.5 * 14.7 * sin(22.5°) ≈ 8.4 N·m.

A 15m Long Dowel Is Pivoted About the End So That