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[Phys-L] What do you call the energy that is not internal Energy?



Brian's response to the question about a bullet embedding itself in a block of wood hit upon another question I had, namely: What do you call the kinetic energy due to the motion of an object as whole, be it rotational or translational, when you want to contrast it with the internal energy of the object? Similarly for the potential energy associated with the position of an object as a whole relative to something external to the object. External energy, as Brian wrote, makes perfect sense to me but I don't recall having heard that expression used that way before. I think macroscopic energy seems to be more common.

-----Original Message-----
From: Phys-l [mailto:phys-l-bounces@mail.phys-l.org] On Behalf Of brian
whatcott
Sent: Friday, February 2, 2018 12:32 PM
To: phys-l@mail.phys-l.org
Subject: Re: [Phys-L] Internal Energy of Wood Taking a Bullet

On 2/2/2018 9:21 AM, Jeffrey Schnick wrote:
When you fire a bullet into a block of wood, while the bullet is embedding
itself in the wood, it is clear that the internal kinetic energy of the wood is
increasing. How about the internal potential energy of the wood? Is it
increasing because chemical bonds are broken, increasing for other reasons,
decreasing because the wood is being compacted bringing the molecules
closer together where they find themselves more strongly bound,
decreasing for other reasons, or staying the same?
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Shear and bending to fracture in the substrate heats it somewhat, increasing
its temperature and increasing the  local  entropy. The recoil may increase its
external kinetic energy as well.

Brian W


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