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Rotational Motion

  • #1

Homework Statement


A tire placed on a balancing machine in a service station starts from rest and turns through 4.9 revolutions in 1.0 s before reaching its final angular speed. Calculate its angular acceleration.

I need my answer in
rad/s^2


Homework Equations


a=w/t
1rev= 2n rad


The Attempt at a Solution


Converted rev/s to rad/s
4.9rev/s * (2n rad/s)/ 1 rev= 30.7876 rad/s

a=w/t
a= (30.7876 rad/s)/ 1sec => 30.7876 rad/s^2

This answer comes out wrong.

What am I doing wrong?
 

Answers and Replies

  • #2
Dick
Science Advisor
Homework Helper
26,258
618
It's not a constant angular velocity question. Angular velocity changes with time, so you can't just use a=w/t. You need a formula analogous to s=(1/2)*a*t^2 for linear motion. It looks very similar, just the meaning of the letters changes.
 
  • #3
Okay thanks. I get it now.
 

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