Angular rotation

  • Thread starter ~angel~
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  • #1
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I've been trying to do this question in the text book, but I can't seem to get the answer.

Emilie's potter's whel rotates with a constant 2.25 rad/s^2 angular acceleration. After 4 seconds the wheel has rotated through an angle of 60.0 rad. What was hte angular velocty of the wheel at the beginning of the 4.00 second interval.

I thought I could use a = (w2-w1)/ (t2-t1), but I end up with 6 as my answer, which is incorrect.

Thank you in advance.
 

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  • #2
SpaceTiger
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Perhaps this thread will help.
 
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Ok, ive got it. But why is my method incorrect?
 
  • #4
SpaceTiger
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~angel~ said:
Ok, ive got it. But why is my method incorrect?
Because:

[tex]\omega_2\ne\frac{\Delta \theta}{\Delta t}=15\ rad/s[/tex]

Actually,

[tex]\bar{\omega}=\frac{\omega_2+\omega_1}{2}=\frac{\Delta \theta}{\Delta t}[/tex]
 

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