What are the tensions in the strings of a 3.60 kg object in circular motion?

AI Thread Summary
In the discussion about the tensions in the strings of a 3.60 kg object in circular motion, participants emphasize the importance of considering both strings when calculating tension. The object rotates horizontally at a constant speed of 7.20 m/s, requiring the application of relevant physics equations. One user struggles with finding the radius and angle, leading to incorrect tension calculations. Others advise drawing a free body diagram to account for the forces acting on the object and to correctly sum the forces in each direction. Properly addressing both tension forces is crucial for solving the problem accurately.
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***circular motion!***

Homework Statement


http://www.webassign.net/pse/p6-11.gif
A 3.60 kg object is attached to a vertical rod by two strings as in Figure P6.11. The object rotates in a horizontal circle at constant speed 7.20 m/s.


(a) Find the tension in the upper string.

(b) Find the tension in the lower string.

Homework Equations



T=mg/costheta
m(v^2/r)=Tsintheta


The Attempt at a Solution



I tried to solve for r and i got 1.32 but when i plugged it into the equation for tension it said it was wrong. i tried to solve for theta and got 41.3 in order to plug into the equation and it was wrong as well. what am i doing wrong??
 
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I think you are forgetting there are two strings. You can't use your equation and do each string separately. You need two different tension forces in your equations. Draw a free body diagram of the ball and sum up the forces in each direction like you would do for any other force problem.
 
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