Angular Acceleration of Electric Motor

[physicsfun_12]

Homework Statement

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.
B) Determine the angular velocity when x=2pi radians. Give your answer in r.p.m.

Homework Equations

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

 

[rock.freak667]

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

if y=t², then your equation becomes:

2π=50y-y²

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

 

[physicsfun_12]

Clever!

Thanks a lot!

Mike