rotational motion problem

Question

The tub of a washing machine is

initially at rest. When the spin

cycle begins, it begins to rotate. In

the first 2.80 s, it makes 3

complete revolutions.

What is its

final angular velocity?

(Unit = rad/s)

Answer 1

You can use the analogy with the kinematic equations of motion. This is a rotational acceleration process and you know t, ω₀ (the initial rate of angular velocity = 0 rad/s), and Δθ = 3 revs = 6π radians

This is like finding v knowing v₀, t, and d: The equation you would need is ((v+v₀)/2)t = d = Δx

The analogous rotational equation is

((ω+ω₀)/2)t = Δθ

zeroing ω₀ and solving for ω:

ω = 2Δθ/t