How heat energy is produced by friction?

Answer 1

In physics, why is always harder to explain than what. To this day, we do not know why gravity attracts mass and space, we just know that it does. Nor do we know why there is quantum jitter at the subatomic level, we just know that there is.

In fact, heat is not generated by sliding friction. Temperature is raised by sliding friction, but temperature is a measure of the average kinetic energies of the atoms and molecules of the material whose temperature we take. In fact what happens is the kinetic energy and work of the mass sliding over the surface against a friction force is transfered in some part to the atoms and molecules of the matter of the surface.

That energy transfer in turn raises the average kinetic energy of the atoms and/or molecules. And we measure that increase as an increase in temperature..typically in degrees Kelvin. It's particle kinetic energy and temperature, not heat, that increases with sliding friction action. But, over time, we've come to call the atomic/molecular kinteic energy heat to show this specific kind of KE can be measured as temperature.

In fact, what we call heat can be best described as a change of heat over time dq/dt ~ del(T); where delT is a temperature difference in degrees K, across some medium through which the heat is changed. How much heat is changed over time also depends on the physical characteristics of the medium; like the specific heat coefficient, the area and thickness, etc.