Let me attempt to present corrected versions of Ludwik's A & B.
A. The puck sliding across the floor with initial ke=K is brought to rest
by the frictional force R.
1. The Work-Energy Principle tells us that: delta(K) = Work done by forces,
assuming no other forms of energy present.
2. Work done by R = -Rx
3. Therefor: 0 - K = -Rx and x = K/R
B. The puck and floor form an isolated system ( no external forces, etc.)
so: delta(U) = 0
1. Therefor if we can enumerate all the categories of energy that might change,
Ui, and since energy is additive:
delta(U1) + delta(U2) +..... = 0
where delta(Ui) = Ui(when ke=0) - Ui(when ke=K)
2. Among the forms of energy to be considered are:
a. bulk Kinetic Energy
b. potential energies that can change due to deformations (eg. scratching
of surfaces, crazing, transfer of material from one surface to another)
c. energy internal to the bodies associated with change of temperature
(used to be called "Sensible Heat")
3. If you wait for the entire system to come to a uniform temperature (still
isolated) AND the change of energy forms b. are NEGLIGIBLE, then
0-K +c*(m+M)*dT = 0
{ I like to represent delta(K) by (0 - K) to remind students that it is a
CHANGE.)
Have the terms "Sensible Heat" and "Latent Heat" disappeared?
As far as "transfer" vs. "transform", I believe we talk of transferring
energy between modes (eg ov vibration), as well as across system boundaries.