posted by Anonymous .
I need help with part b... I found in part a that delta L is .29568m and I think I might be doing something wrong with the units because I can't get the right answer.
A 156 g hockey puck is attached to a rubber band and rotated with an angular speed of 12.8 rad/s on frictionless horizontal ice. It takes a force of 1.12 N to stretch the rubber band by 1 cm.
(a) If the original length L of the rubber band is 1 m, by how much (in m) will it be stretched by the rotation?
Delta L = .29568m
(b) How much energy do you need to start the stone from rest and rotate as in part (a) with an angular speed of 12.8 rad/s? Neglect the mass of the rubber band.
Etotal = J
HELP: Add up the kinetic energy and the elastic potential energy.
HELP: Ekin = 1/2*m*v2, with v = length*omega.
Remember again to use the stretched length:
Eelast = 1/2*k*(Delta L)2