Some of it is transformed into heat and noise, but where does the rest go?
Further details: The object does not bounce off (e.g. a sack of rice marble ball). The hand remains completely static throughout the process.
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Qmechanic
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Šime Vidas
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Depends on how elastic your arm is... with some training humans can store some (but not a lot) of energy in form of potential energy in the elasticity of their tissues. – CuriousOne Dec 20 '14 at 00:21
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@CuriousOne I’ve added a few more details, but I don’t think that potential energy is a factor in this. – Šime Vidas Dec 20 '14 at 00:24
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The potential energy in the tissue elasticity of your hand/arm is... unless, of course, you are a man of steel who doesn't bend, at all. In that case all the energy would go into noise and heat, like you said. – CuriousOne Dec 20 '14 at 00:29
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@CuriousOne Ah I see. I misread. So, colloquially speaking, the hand absorbs the energy? – Šime Vidas Dec 20 '14 at 00:30
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1Yep. And if the object is too heavy, the hand breaks, which is ultimately also a way of absorbing energy, just not in a good way... – CuriousOne Dec 20 '14 at 00:33
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"where does its kinetic energy go?" into other forms of energy (essentially, by definition). Power is, essentially, the flow of energy of one form to another. Of course, these other forms of energy may be obvious or not. – Alfred Centauri Dec 20 '14 at 00:43
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There is no "rest", you mentioned all energy destinations. If you will catch energy silently, it will go only into heat. – Dims Dec 20 '14 at 03:48
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5Possible duplicate of if a body is stopped by means other than friction, where does energy go? – Adi Ro Jan 21 '16 at 18:48
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You're making a mistake in assuming that there is any left. Heat and sound account for all of it.
There is one exception, though. If it crashes into something, and that breaks or bends the object, then the potential energy of the molecules is higher.
That's why cars end up smashed after a collision. The molecules of the metal or plastic or whatever have more chemical potential energy in the deformed state (actually, less negative potential energy.)
anotherguy
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I’ve added more details. A marble ball will not deform, and if aimed perfectly, the ball will land in the center of the hand and stop moving immediately. My guess is that the hand (its skin and muscles) absorbs the energy. – Šime Vidas Dec 20 '14 at 00:29
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the marble does not deform but the hand does. The tissues in the hand absorb the marble's kinetic energy until they reach their compression limit, then the bones and muscles of the arm take the rest. If the hand is rigid the marble would bounce. – paul Dec 20 '14 at 00:52
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@ŠimeVidas Yes, the marble does deform a small amount, although it returns to its normal shape. Nothing is perfectly rigid. Everything has a small amount of elasticity, because there's space between the molecules. – anotherguy Mar 14 '15 at 02:21
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Assuming that hands remain completely static, and the object do not breaks, then all of its energy can be considered to be converted into heat and sound (as you have already described).
Al Khwarizmi
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Energy is accepted by molecules of both objects and turns into heat form.
Dims
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OP already mentions heat as one source of energy, so this really doesn't address the issue. – Kyle Kanos Dec 20 '14 at 03:21
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Heat is not a source but destination. It is the main and unavoidable destination of energy while catching a body. One can catch a body without any other energy transform, but it will always transformed into heat. Heat is energy's always final grave. – Dims Dec 20 '14 at 03:44
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I can understand your confusion, but I wrote that meaning heat is the source for where the energy goes, not source of energy into the system. Anyways, this still doesn't address OP's issue. – Kyle Kanos Dec 20 '14 at 04:06