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Old Dec 25th 2012, 10:27 PM   #1
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When does an object leave its cirular motion

Hey guys i have this question in my physics assignment and i dont really get my teacher's answer. I would really appreciate some help.

The question goes something like this: a star rotates about its axis with a period of 0.21s. Using the answers you have obtained for the gravitational field strength of the star and the centripetal acceleration of a particle moving in a circular path of radius 1.7 x 10^4m and with a period of rotation of 0.21s, suggest whether particles on the surface of the star leave the star due to the high speed that the star rotates at.

Ans: Since the acceleration of free fall (1.2 x 10^12 ms^-2) is much larger than the centripetal acceleration (1.5 x 10^7 ms^-2), the gravitational pull is more than what is required to provide the centripetal force. Therefore, the particles will not leave the star.

Ok guys, this is the part i dont get. If the star's gravitational pull provides the centripetal force for the particles to stay on the star, how do u know when the particles will leave star?
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Old Dec 28th 2012, 06:53 AM   #2
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If the centripedal acceleration for a particle on the surface of the star is greater than the acceleration due to gravity, then the particle would be flung away off the surface. Sort of like swinging a ball on a tether in a circular motion around your head - if the tether isn't strong enough to sustain the centripedal force of the ball, it will break and the ball will be flung away from you.
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Old Dec 28th 2012, 07:48 AM   #3
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Oh ok thanks a lot! Finally got it.
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centripetal acceleration, centripetal force, circular motion, cirular, gravity, leave, motion, object, satellite



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