Angular momentum and tension of string

AI Thread Summary
The problem involves a 3kg puck revolving in a circle with a radius of 0.50m, attached to a string. The angular momentum is given as 3kg(m^2/s), leading to the calculation of linear velocity using the formula L = mrv. The initial calculation mistakenly used a radius of 0.25m, resulting in an incorrect tension value. The correct tension in the string, considering the proper radius, is calculated to be 192N. The discussion emphasizes the importance of using the correct radius for accurate results.
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This problem is baffling me.

A 3kg puck revolves in a circle on a frictionless table at the end of a 50cm long string. The puck's angular momentum is 3kg (m^2/s). What is the tension in the string?

This what I did
L= mrv
therefore
3kg*.25m*v = 3kgm^2/2
v=4m/s
F=(mv^2)/r
(3kg*16m/s)/(.25m) = 192N

is this right?
 
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r should be 0.50 m, not 0.25.
 
I agree with arildno, the string is acting as the radius of the circle itself, not as the diameter :smile:
 

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