what happens to the mechanical energy of freely rotating shaft .?friction and heat r not d maater..?

Question

If law of conservation of energy is true ..what happens to the mechanical energy of freely rotating shaft .??
if we start an egine and allowed to run.here the chemical energy of fuel is converted into heat.further this heat energy is converted into mechanical energy of rotating shaft.if this shaf is connected to a generator it will produce electric energy & if connectd to pump it will lift fluid.what happens to that energy if we leave that shaft rotate free with out using..is that entire enrgy transferred to AIR surrounding shaft...?????? heat and friction may not be the answers as they exist all the time, no matter we r utilising the energy or not.

Answer 1

To be more specific, the energy of the shaft is transferred to the surrounding air and anything else that is in contact with the shaft. The shaft will drag air at its surface and transfer motion to the air, so the air will gain kinetic energy from the shaft. In addtition, there will be friction between the air and the shaft and the shaft and its bearings that will produce heat. This will raise the temperature of the air, and the energy contained by the air will be its specific heat times the temperature rise. The heat generated by bearing friction will raise the temperature of the bearing mounts and that will account for additional energy lost by the shaft, also the specific heat of the bearing material times its temperature rise. Eventually, the bearings will heat the surrounding air and anything else in contact with it, and all of these things will receive the energy lost by the shaft. Wait long enough and that energy will be distributed thoughout the universe, but is never lost. Once in the form of heat, that is the way it stays. Yes, the heat exists all the time, but not in the same amount. The flywheel eventually increases the heat content of the universe.

Answer 2

I think you might be confusing Work with Energy...
But in any case, the wording of this Q is funny... If you had a ball at the top of the hill and then let it roll down the hill, would you ask were the energy went???
You are converting fuel (potential energy) into kinetic. Part of that kinetic energy is observed as the rotating shaft... Yes, balls roll down hill! And you are asking where the energy went as the ball rolled down the hill?
An object with constant mass is in free fall, the total energy of position 1 will equal that of position 2.
(Ek+Ep)1 = (Ek+Ep)2
At the bottom of the hill (when the fuel runs out), most of the potential energy has been turned into kinetic, what happens to the ball? It keeps rolling! However, on a clean flat surface it will eventually stop due to friction (air and rolling).

Answer 3

The fuel ( energy) is supplied to the motor. It is used up by the motor.

The motor supplies the energy to the shaft.

You can capture the energy of the motor from the shaft.

If you chose not to run some thing from the shaft the energy used to run the engine is just wasted.

If it was truly a freely rotating shaft the motor couldn't transfer energy to the shaft. To transfer energy the shaft has to be fixed to the motor.

Answer 4

if that shaft is left rotating then the rotating shaft will cause the air near it to flow and this will give mechanical energy to air . no matter the amount of energy is small but still it is the conversion of energy