but we don’t think of a tennis ball falling in a vacuum as gaining thermal energy or rising in temperature.
That’s because temperature is a characteristic of a multi-particle system. One single particle has energy, a large set of many particles has temperature.
And still speaking of high-school physics, conversion between thermal and kinetic energy is trivially easy and happens all the time around us.
A tennis ball is a multi-particle system; however, all of the particles are accelerating more or less in unison while the ball free-falls. Nonetheless, it isn’t usually considered to be increasing in temperature, because the entropy isn’t increasing much as it falls.
That’s because temperature is a characteristic of a multi-particle system. One single particle has energy, a large set of many particles has temperature.
And still speaking of high-school physics, conversion between thermal and kinetic energy is trivially easy and happens all the time around us.
A tennis ball is a multi-particle system; however, all of the particles are accelerating more or less in unison while the ball free-falls. Nonetheless, it isn’t usually considered to be increasing in temperature, because the entropy isn’t increasing much as it falls.