The principle of the conservation of energy tells us that energy is never lost, but only changes from one form to another. Yet in many ordinary situations, energy may appear to be lost. In each case, explain what happens to the “lost” energy.

(a) A box sliding on the floor comes to a halt due to friction. How did friction take away its kinetic energy, and what happened to that energy?

(b) A car stops when you apply the brakes. What happened
to its kinetic energy?

(c) Air resistance uses up some of the original gravitational potential energy of a falling object. What type of energy did the “lost” potential energy become?

(d) When a returning space shuttle touches down on the runway, it has lost almost all its kinetic energy and gravitational potential energy. Where did all that energy go?