Ball on a string (vertical circle)

AI Thread Summary
The discussion revolves around calculating the tension in a string when a 500 g ball moves in a vertical circle. At the top of the circle, the calculated tension is 9.15 N, and at the bottom, it is 28.7 N, but these values are incorrect. The tension must account for the gravitational force acting on the ball, which requires a different approach to the calculations. A force diagram is recommended to clarify the forces at play. The original poster has not engaged in the forum for over a decade, indicating a lack of follow-up on the issue.
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Homework Statement


a 500 g ball moves in a verticle circle on a 1.01 m long string. if the speed at the top is 4.3 m/s, then the speed at the bottom will be 7.62 m/s. what is the tension of the string when the ball is at the top? when is the tension of the string when the ball is at the bottom?


Homework Equations


tension = (Fnet)=mv2/r


The Attempt at a Solution


top:
tension = (Fnet)=(0.5 kg)(4.3)2/(1.01) = 9.15 N

bottom:
tension = (Fnet)=(0.5 kg)(7.62)2/(1.01) = 28.7 N

these answers are wrong, however. and I'm not exactly sure why.
pointers in the right direction would be much appreciated!
 
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The numbers you found were the magnitudes of the force pointing directly outward from the string, but that is not the tension in the string. Use the gravitational force on the ball to solve for the tension in the trope. Drawing a force diagram will make this problem more understandable.
 
@Engineering_PHY123 - this thread was started more than 11 years ago. The OP has not visited PF for more than 10 years.
 

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