(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

A 2.5 kg pulley of radius 0.15m is pivoted about an axis through its center. What constant torque is required for the pulley to reach an angular speed 25rad/s after rotating 3.0 revolutions, starting from rest?

2. Relevant equations

torque = (mr^2)(angular acceleration)

3. The attempt at a solution

First I solved for time using t= omega/angular speed = 6(pie) rad / 25 rad/s = 0.75s.

Then, I solved for angular acceleration = 33 rad/s

Solving for torque, using the above equation, I got 1.9 m-N

The textbook I have says this is the wrong answer. What have I done?

The book says the answer is 0.47 m-N

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# Homework Help: Rotational Motion and Equilibrium

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