O
one.skilled
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A puck of mass m is attached to a cord passing through a small hole in a frictionless, horizontal surface. The puck is initially orbiting with speed vi in a circle radium ri. The cord is then slowly pulled from below, decreasing the radius of the circle to r. (A) what is the speed of the pick when the radius is r? Answer: vf = (vi*ri)/r. (B) Find the tension in the cord as a function of r. Answer: T = F = ma(centrip) = m(vf^2)/r = m(vi * ri)^2/r^3. (C) How much work W is done in moving m from ri ti r? Answer: 1/2m(vi^2)(ri^2/r^2 -1). I have no idea how they got there.