Question

A wheel with rotational inertia i is mounted on a fixed, frictionless axle. the angular speed ω of the wheel is increased from zero to ωf in a time interval t. what is the average net torque τ on the wheel during this time interval?

Answer 1

According to Newton's second law:
τ = Iα, where I is the moment of inertia and α is the angular acceleration.
Angular acceleration can be written as:
α = (ωf - ωi) / t
α = ωf/t

Substituting into the second law:
τ = Iωf/t