Which layer is broken up into several plates which "move and float very slowly? Their very slow motion is the cause of plate tectonics, a process associated with continental drift, earthquakes, volcanoes, and the formation of mountains.

Two masses are connected by a rope that hangs over a pulley as shown below. the pulley is a uniform cylinder of radius 푅=0.381meters and mass 푀=3.1푘푔. initially 푚"is on the ground and 푚#rests 2.5 meters above the ground. if the system is released, use conservation of energy to determine the speed of 푚#just before it strikes the ground. assume the pulley bearing is frictionless.