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Math Help - Could you help me review and check my physics homework?

  1. #16
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    Re: Could you help me review and check my physics homework?

    Turned out the task said it was r=0.1, not d=0.1, my bad Then, we have 3130rad/s which is around 31300rpm, right?

    Also, I spotted that in 3. there IS a mistake - namely, I'm using 150cm (the diameter) as the radius which ruins the final answer. It should be cirmuference = 471cm and then 20.1rad/s as a consequence, shouldn't it?
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  2. #17
    MHF Contributor ebaines's Avatar
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    Re: Could you help me review and check my physics homework?

    Quote Originally Posted by Glyper View Post
    Turned out the task said it was r=0.1, not d=0.1, my bad Then, we have 3130rad/s which is around 31300rpm, right?
    To convert radians/second to RPM you need to multiply by 60 seconds/minute and divide by 2  \pi radians per revolution. You should get an answer a bit less than 30,000 RPM

    Quote Originally Posted by Glyper View Post
    Also, I spotted that in 3. there IS a mistake - namely, I'm using 150cm (the diameter) as the radius which ruins the final answer. It should be cirmuference = 471cm and then 20.1rad/s as a consequence, shouldn't it?
    I get precisely 20 rad/s. An easy way to do this is to use the fact that liinear velocity and rotational velocity are related by v=\omega R. Here  v= 15 m/s and  R= 0.75m, so

    \omega = \frac {15 \frac m s}{0.75 m} = 20/s
    Last edited by ebaines; October 16th 2012 at 11:51 AM.
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  3. #18
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    Re: Could you help me review and check my physics homework?

    OK, I think I get it. Thank you a lot for all your help
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