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Rotationlal dynamics quest

  • Thread starter bigbuck
  • Start date
6
0
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While i have done the work and believe i have followed the equations, I'm not confident of my answer as I dont understandt the relationship between the units im using. While Im pretty sure KE shoudl be in joules. I am guessing in the end.

the question:
Calculate the kinetic energy of a 1.00kg bicycle wheel with a diameter of 72.0cm when it is spinning about its axle at 180rpm. Assume that all the mass of the wheel is concentrated at its perimeter.

my answer:
KE=.5*I*om^2
I=m*r^2 1.00kg*(.360m)^2 = .130kg*m^2
omega = 180rev/m*6.28rads/60sec=18.84rad/s
.5*.130kg*m^2*18.84rads/s=1.22J

thanks
 

Answers and Replies

Kurdt
Staff Emeritus
Science Advisor
Gold Member
4,769
6
You forgot to square the angular velocity. The units are fine.
 
6
0
thanks!
much appreciated
 

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