Generic Question

[hydromech]

To anyone who knows the answer...

It is said that energy cannot be created or destroyed, only transformed into another state.

My question is...into what form is kinetic energy transfered?

A wheel for example...you push it and it moves. You have transfered energy into it. It stops rolling because its energy has gone...yes...but gone where. The wheel is not hot and its making no noise. It's still and quiet...where has the 50 joules I have just given it gone to?

I am not challanging the fundamentals of physics here I just wondered thats all.

Thanks

Hydromench
Hydraulic systems Engineer

 

[rb1957]

friction, air resistance ...

 

[hydromech]

Thanks rb...

That answer in itself brings many more questions to mind...

I'll end it there...

Thanks again..

Hydromech

 

[rmw]

It is making noise, you just can't hear it, and probably don't have instruments accurate enough to measure it, and it is heating up, same problem with measuring it.

Push that wheel out of the hatch of the space shuttle right at the point of re-entry to the earth's atmosphere, and what happens to it?

rmw

 

[rb1957]

the shuttle would burn up ?

no, i know what you mean rmw ... but i'd used an orbiting shuttle for the example (ie of a frictionless, vaccuum environment) ... this is why satellites use momentum wheels for stability (... 'cause they run, but only after a VERY long time)

 

[quark]

Energy can, broadly, be classified into available and unavailable energy. The available kinetic energy subsequently gets converted into unavailable heat energy via friction, as already suggested by RMW, and gets dissipated into the atmosphere, which is called as sink. Then you have the air resistance to overcome.

The wheel or any of its components become hot if and only if the rate of heat dissipation is less than rate of heat generation.

 

[imok2]

The First Law of Thermodynamics tells us that all of the previously potential energy that came out of a battery and out of a dancer's muscle cells doesn't go away to the mysterious dimension of nothingness. It has to still be around somewhere. Where is that somewhere? It all ends up as a slight increase in the energy of air molecules.

Yes, it actually heats up the air a little bit. A little bit warmed the battery, then flowed into the air. A little bit warmed the wires, then flowed into the air. A spinning cd and motor does work on some air molecules, causing them to zip around faster and transfer their newly increased kinetic energy to still more air molecules. The cells in your body gave off heat which flow out of your body into the air. Your dancing limbs also push billions of air molecules out of the way. All of that heat and motion is eventually transferred to the air, slightly increasing the energy of billions of air molecules. After that it is radiated out into space where it will help to warm up the universe an itsy-bitsy, teensy-weensy little bit.

 

[unclesyd]

OH NO! Space warming is upon us.

 

[waross]

Pushing a little wheel a little way is not much work and will not heat it up very much. Try rubbing your hand rapidly back and forth on your desk-top until you can feel a little warmth. The amount of work that you have to do to feel a litle heat will explain why you don't notice the heat from the wheel.
For a good example of kinetic energy being converted into heat energy, check the brake drums of a loaded truck that has just made a panic stop from 55 MPH, or better yet, at the bottom of a long hill. Several generations ago, in the Pacific Northwest, the logging trucks carried large water tanks. The water was piped to each brake drum. On a long down grade, the driver would turn the water on to cool the brakes. More accurately, the driver turned the water on while the drums were still cool to avoid cracking the drums.
When the drums heated up, there would be a cloud of steam issuing from each brake drum. A driver I knew years ago was smokin’ down a very long hill on the highway in a cloud of steam. He didn't realize that one water line had plugged up and one wheel was running dry. The brake drum got so hot that it set fire to his tires. He got to a water hose in time to save the load of logs, but he lost the tires.
Yup, kinetic energy will definitely produce heat energy.
yours

 

[yourshadow]

very interesting))))

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http://oil-gas-minerals.com

 

[25362]

Back to the original question. The wheel stops mainly because of the action of nonconservative forces of friction: against the floor and the air drag.

 

[0707]

Energy loss is directly proportional to surface roughness, air resistance and friction.