In the system of two blocks and a spring shown above, blocks 1 and 2 are connected by a string that passes over a pulley. The initially un-stretched spring connects block 1 to a rigid wall. Block 1 is released from rest, slides to the right and is eventually brought to rest by the spring and by friction on the horizontal surface.
Which of the following is true of the energy of the system during this process?
(A) The total mechanical energy of the system is conserved.
(B) The total mechanical energy of the system increases.
(C) The energy lost to friction is equal to the gain in the potential energy of the spring.
(D) The potential energy lost by block 2 is less in magnitude than the potential energy gained by the spring.
(E) The potential energy lost by block 2 is greater in magnitude than the potential energy gained by the spring.