question_answer 56)

                  A body falls towards earth in air. Will its total mechanical energy be conserved during the fall? Justify.                

Answer:

                  Total mechanical energy is conserved only if conservative force acts on the system. In this case, force of friction due to air also acts on the falling body in addition to the conservative force (i.e., gravitational force). Hence, total mechanical energy of a falling body is not conserved.