At the top of a roller coaster you have 90j of potential energy and 10 j of kinetic energy at the bottom of the roller coaster you now have 90j of kinetic energy how much potential energy do you have at the bottom of the coaster?

Two steel balls, each of mass m, are welded to a light rod of length l and negligible mass and are initially at rest on a smooth horizontal surface. a horizontal force of magnitude f is suddenly applied to the rod as shown. determine (a) the instantaneous acceleration a of the mass center g and (b) the corresponding rate at which the angular velocity of the assembly about g is changing with time.