PHYS 2101 Lecture : Lecture21
Document Summary
A gure skater stands on one spot on the ice (assumed frictionless) and spins around with her arms extended. Since angular momentum is conserved, when she pulls in her arms, her moment of inertia decreases and her angular velocity increases. Compared to her initial rotational kinetic energy, her rotational kinetic energy after she has pulled in her arms must be: Smaller, because her moment of inertia is smaller. Bonus: where did the energy come from? so k f > ki. *note we are only covering parts 12. 1-12. 5 of this chapter. Equilibrium: these objects look like they are about to fall but they don"t. No linear acceleration, no angular acceleration net = L d dt: must have vanishing net external force and net external torque! net = 0. This means they could also be moving at constant speed, or rotating at constant speed. F(x) = " du (x) dx x2, x3, and x4: equilibrium (f=0 there)
