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ronynelson28@yahoo.com

Joined: 13 Mar 2012
Posts: 1
Location: woobridge

 Posted: Tue Mar 13, 2012 8:34 pm    Post subject: CIRCULAR MOTION 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?
hepcj

Joined: 23 Jun 2007
Posts: 125

 Posted: Thu Mar 15, 2012 8:04 pm    Post subject: 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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