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CIRCULAR MOTION

 
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ronynelson28@yahoo.com



Joined: 13 Mar 2012
Posts: 1
Location: woobridge

PostPosted: Tue Mar 13, 2012 8:34 pm    Post subject: CIRCULAR MOTION Reply with quote

I'M HAVING trouble finding the radius for my question


A rock on a string is swung in a circle. The centripetal acceleration of the rock is 5.21 meters per second square. The time period for one rotation is 5.5 seconds.

What is the length (radius) of the string?
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hepcj
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Joined: 23 Jun 2007
Posts: 125

PostPosted: Thu Mar 15, 2012 8:04 pm    Post subject: Reply with quote

With this question you need to consider the centripetal force
F = m*r *omega^2
and this force is equal to = m a
equating

m a = m r omega^2

the mass cancels to give,

a = r omega^2 -----(1)

The period in terms of omega is T = 2 pi omega
which means omega = T/(2 pi)
then substitute into (1)

This gives a = r (T/(2 pi))^2 = r T^2/(4*(pi^2))
now you have everything you need to calculate the radius r if you rearrange to make r the subject in terms of a and T.
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