Assignment 1.1: A
pulley of radius 0.9 m is used to lift a bucket from the well. If it took 3.6
rotations for the pulley to take water out of the well, how deep is water in
the well?
Solution
Now one rotation = 2π rad, therefore, we can calculate the angle traversed by the pulley in 3.6 rotations, which is 3.6 × 2π = 3.6 × 2 × 3.14 = 22.608 rad. Since s = rθ, this implies the corresponding length of the arc (linear distance), s = 0.9 × 22.608 = 20.3 m.