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Vitani11
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Homework Statement
A particle of mass m is moving on a frictionless horizontal table and is attached to a massless string that passes through a tiny hole of negligible radius in the table, and I am holding the other end of the string underneath the table. Initially the particle is moving in a circle of radius r0 with angular velocity ω0, but I now pull the string down until the radius reaches r. Assuming that I pull the string so slowly that we can approximate the particle’s path by a circle of slowly shrinking radius, calculate the work I did by pulling the string, and compare it to your answer in (5.1).
Homework Equations
W = ∫F⋅dr
Answer for KE is [(mωo2ro2)/2]((ro/r)2-1)
The Attempt at a Solution
W = ∫F⋅dr = ∫mv2/r dr= ∫mω2rdr = (mω2/2)(r2-ro2)
From conservation of angular momentum I get that ω = (ωoro2)/r. replacing this with the result gives (mωo2ro4)/2[((ro/r)2-1)] and the units don't check out. Shouldn't this be the same as KE?
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