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In an inelastic collision betweentwo objects, what exactly causes the system composed of the two objects to lose mechanical energy into heat?

I was trying to answer this question using the work energy theorem by setting the work done by the internal forces that both objects exert on one another to the change in kinetic energy of the two body system. I applied this to two different scenarios. In the first, object 2 is more massive than object 1. In the second, object 1 and object 2 have the same mass. Also, object 2 has an initial velocity of zero. If both masses are different, I believe that the work done by each internal force differs (the more massive object causes the least massive object to be displaced more in comparison to how much the more massive object is displaced by the least massive object). This is what I saw as what causes such a loss of kinetic energy. Is the answer to this question beyond introductory Newtonian mechanics? Is my method correct?

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By definition, an "inelastic collision" means that part of the kinetic energy possessed by the colliding objects is lost by performing (irreversible) internal work on the objects during the collision, and is therefore not carried away as kinetic energy when the objects rebound off each other. You can easily visualize this if the colliding objects are soft lumps of clay, for example. Some of the collision mechanical energy, as you call it, gets used to plastically deform the clay during the collision, which then shows up as a slight increase in the temperature of the clay itself.

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  • $\begingroup$ The above method I mentioned before is true and I have verified it. My question is what if two masses of equal mass take part in an inelastic collision? What causes this loss of heat? $\endgroup$ Nov 6, 2017 at 18:59
  • $\begingroup$ are they both going the same speed? $\endgroup$ Nov 6, 2017 at 19:02
  • $\begingroup$ The first mass is moving to the right and the second mass is at rest and it is to the right of the first mass. $\endgroup$ Nov 6, 2017 at 19:16
  • $\begingroup$ then the center of mass after the collision will be moving to the right, and by knowing the velocity of the merged clay lump, its momentum can be solved for. Knowing the momentum of the moving lump prior to the collision, the momentum difference lets you solve for the amount of energy converted into heat. the heat thus generated comes from the internal friction of the clay particles sliding against each other while they are being deformed. $\endgroup$ Nov 6, 2017 at 19:46
  • $\begingroup$ I believe I now have an answer to my question. Thank you! $\endgroup$ Nov 6, 2017 at 19:52

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