A spring with spring constant 72 N/m has one end attached to a peg on a horizontal surface, and another attached to a puck with mass of 0.34 kg that can slide on the surface. The relaxed length of the spring is 0.12 m. It is desired to put the mass into motion so that it rotates with constant speed at a radius of 0.28 m. (a) How fast does the puck need to move to make this possible. Ignore friction for this part of the problem. (b) Some 30 s later, the puck is observed to be going in a smaller circle of radius 0.22 m. Apparently it was not a perfect approximation to neglect friction after all! Find the work done by friction during the 30 s. Assume that we can still approximation the motion as circular in the final situation, even though friction is gradually slowing it down.
a) velocity = 3.08 m/s b)... View the full answer