I read a paragraph on the transfer of potential energy to kinetic energy and heat from this website:
Even if air resistance slows down the ball, the potential energy is
the same (Mb x g x H). But if air resistance is in the way, not all of
the potential energy can be converted to kinetic energy. Some of the
energy has to be used to push the air molecules out of the way. When
that happens, the energy of the air molecules is increased. The air is
actually "heated" up by the falling ball.
This text indirectly mentions that the Potential Energy gets converted into heat. However my common sense (for lack of a better term) makes me think that the Potential Energy gets converted into Kinetic Energy which in turn gets converted into Thermal energy. Would someone be able to enlighten me on this please?
Also, as a side question, it isn't called Heat Energy right? A lot of websites seem to be saying that, but heat is just the transfer of Thermal Energy…
Best Answer
The friction with the air indeed slows down the falling ball. The friction is minimal if the ball stays in place (i.e. there may be only some friction due to air currents.) But if the ball moves the friction is bigger because as the ball moves, it pushes away the air molecules to make room. The friction opposes the ball movement. So, indeed, the heating takes from the kinetic energy through friction, not from the potential energy. The meaning of the text, as I understand, it that, bottom line, the kinetic energy acquired by the ball during its fall is not equal to the total potential energy $M_b gH$.