A painter on a scaffold drops a 1.50-kg can of paint from a height of 6.00 m. (a) What is the kinetic energy of the can when the can is at a height of 4.00 m? (b) With what speed will the can hit the ground? (Neglect air resistance.) (c) Show that the expression for speed from energy considerations is the same as that from kinematics (Section 2.5).
THINKING IT THROUGH. Total mechanical energy is conserved since only the conservative force of gravity acts on the system (the can). The initial total mechanical energy can be found, and the potential energy decreases as the kinetic energy (as well as speed) increases.