When does a bob attached to a string become slack???When mgcos@ = mv^2/r?
When doing what? You're going to have to provide a bit more information about what the bob on the string is doing?
It depends if you are restricting the angle to be below 90 degrees or if you may go above.
The equation (for theta smaller or equal to 90 degrees) is
T - mg cos theta = m v^2/R
The rope becomes slack if T=0.
what can you say about theta and v in that case?
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