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Re: [Phys-l] momentum and energy



Neither do I -- It took some time for me to remember writing the below. I think I've had a minor (Laudate Deum.) stroke. Furthermore, it took me a while to find the reply key strokes.

bc

p.s. maybe I meant identically? -- can elasticity (100%) exist w/o conservation of KE. (This is w/o thinking.)

Jack Uretsky wrote:

They are cetainly equivalent. I don't know what is meant by "analytically the same".
Jack


On Mon, 13 Nov 2006, Bernard Cleyet wrote:


"... note that you do not need the elasticity condition if you conserve
kinetic energy
regards,
Jack"


Are they not analytically the same?


bc



Jack Uretsky wrote:


Hi-
consider a 1-dimensional elastic collision between a mass m and a
mass M, M>m, M at rest before the collision, so that m reverses direction
as a result of the collision. Conserve energy and momentum. How much of
the energy does M acquire as M become very, very, very large?
note that you do not need the elasticity condition if you conserve
kinetic energy
regards,
Jack





On Sun, 12 Nov 2006, Spencer, Rob wrote:




Greetings,
I am a high school teacher and I have a question regarding an assumed elastic collision. Suppose a golf ball strikes a massive wall and recoils with a velocity equal in magnitude to its initial velocity. If one were to evaluate the situation with conservation of energy, then energy is conserved (defined to be perfectly elastic). All of the (kinetic) energy remains in the golf ball. None is transferred to the wall. However, the wall must acquire momentum due to the fact the system momentum must be conserved. So the wall has final momentum when it initially had none but has no kinetic energy. I am having a hard time with an object having momentum but no energy conceptually...any guidance would be appreciated.
Regards,
Rob Spencer
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_______________________________________________
Forum for Physics Educators
Phys-l@carnot.physics.buffalo.edu
https://carnot.physics.buffalo.edu/mailman/listinfo/phys-l