**Part B**

From the law of conservation of energy:

mgh = mgh/3 + mgh'

A block of mass *m* slides at a speed *v* along a horizontal, smooth table. It next slides down a smooth ramp, descending a height *h*, and then slides along a horizontal rough floor, stopping eventually. Assume that the block slides slowly enough so that it does not lose contact with the supporting surfaces (table, ramp, or floor).

You will analyze the motion of the block at different moments using the law of conservation of energy.

Part B

Suppose the potential energy of the block at the table is given by *m**g**h*/3. This implies that the chosen zero level of potential energy is __________.

a. a distance h/3 above the floor

a. a distance h/3 below the floor

a. a distance 2h/3 above the floor

a. a distance 2h/3 below the floor

a. on the floor

Part C

If the zero level is a distance 2*h*/3 above the floor, what is the potential energy *U* of the block on the floor? Express your answer in terms of some or all the variables *m*, *v*, and *h*and any appropriate constants.

Part D

Considering that the potential energy of the block at the table is *m**g**h*/3 and that on the floor is ?2*m**g**h*/3, what is the *change* in potential energy? *U* of the block if it is moved from the table to the floor? Express your answer in terms of some or all the variables *m*, *v*, and *h*and any appropriate constants.