# Homework Help: Angular Acceleration of Electric Motor

1. Jan 18, 2010

### physicsfun_12

1. The problem statement, all variables and given/known data
An electric motor starts from rest at time t=0. Its angular velocity is: w=100t-4t3

A) If the angle of rotation, x, of the motor is also zero when t=o, determine an expression for this angle in terms of t.

2. Relevant equations

3. The attempt at a solution
For A) I thought you just integrate the expression given for angular velocity so i got x=50t^2-t^4.

For B), I said that x=2pi, so 2pi=50t^2-t^4 but I am unsure how to solve this for x.

Any help much apriciated,

Mike

2. Jan 18, 2010

### rock.freak667

if y=t2, then your equation becomes:

2π=50y-y2

I think you can solve for 'y' now and then find 't'

3. Jan 18, 2010

Clever!

Thanks alot!

Mike