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Rotating object: Finding Tension and Vtheta

  • Thread starter bjno8
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1. Homework Statement
A string with 2kg mass m on the end is connected to a bar that rotates at a constant rate (theta dot). The string makes a constant angle beta, = 60 degrees relative to the horizontal plane. Find theta dot and the tension force in the string.


2. Homework Equations



3. The Attempt at a Solution

I realize this may be very difficult to understand without a picture, but the rotation is in the x y direction I suppose and gravity is acting downward in the Z direction. I'm not really sure how to go about this problem. There's a specific velocity that will give the angle relative to the x axis the 60 degrees but I'm quite stuck, any help would be great.
 

Answers and Replies

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Maybe this is right?

Ok so after fighting through it again, I realized what might work...

F(z) = 0; Tcos(30) - 2kg*9.81 = 0: T = 22 N

F(n) = ma(n); 22sin(30) = 2(v^2/1.57)

I realized I also forgot to mention the p value: 1.57
 
PhanthomJay
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Ok so after fighting through it again, I realized what might work...

F(z) = 0; Tcos(30) - 2kg*9.81 = 0: T = 22 N

F(n) = ma(n); 22sin(30) = 2(v^2/1.57)

I realized I also forgot to mention the p value: 1.57
Looks good so far. The solution of the 2nd equation will give you 'v'. After determining what 'v' represents, you must now determine theta dot.
 

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