Force needed to pull the string

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The discussion focuses on a mass M revolving on a string through a ring, with gravity neglected. As the string is pulled at a constant velocity V, the radial distance to the mass decreases, prompting the need to analyze the forces involved. A force diagram is required to derive a differential equation for the angular velocity W. The participants aim to determine the function W(t) and the force necessary to pull the string. The conversation emphasizes the mathematical modeling of the scenario and the application of physics principles to solve the problem.
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A mass M whirls around on a string which passes through a ring .Neglect gravity.Initially the mass is distance Ro from the center and is revolving at angular velocity Wo.The string is pulled with constant velocity V starting at t=0 so that the radial distance to the mass decreases.Draw a force diagram and obtain a differential equation for W.Find
(1) W(t)
(2) the force needed to pull the string
 
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