W is the work done on the system, K, U, and Eth are the kinetic, potential, and thermal energies of the system, respectively. Any energy not mentioned in the transformation is assumed to remain constant; if work is not mentioned, it is assumed to be zero.
Select a specific example of a system with the energy transformation shown.
K→ΔEth

a. A wood block sliding across a rough horizontal surface and slowing to a stop.
b. A block sliding on level ground, to which a cord you are holding on to is attached.
c. A wood block moving across a horizontal rough surface at constant speed.
d. A wood block sliding down a rough inclined surface at a constant speed.