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Re: [Phys-l] momentum and energy



The kinetic energy of an object (treated as a particle) can be written as (p^2)/(2M),

E goes to 0 as M approaches infinity.

Al Bachman
----- Original Message -----
From: Spencer, Rob<mailto:spencerr@wl.k12.in.us>
To: phys-l@carnot.physics.buffalo.edu<mailto:phys-l@carnot.physics.buffalo.edu>
Sent: Sunday, November 12, 2006 9:16 PM
Subject: [Phys-l] momentum and energy


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