linear momentum conservation vs mecanical energy conservation


by jaumzaum
Tags: conservation, energy, linear, mecanical, momentum
jaumzaum
jaumzaum is offline
#1
Sep7-11, 09:06 PM
jaumzaum's Avatar
P: 246
A ball A (mass ma) with initial velocity v colides with a ball B (mb) initially stopped. A and B gets the same direction/velocity v', Calculate v'

By linear momentum conservation
ma.v = (ma + mb).v'
v' = mav(ma + mb)

But by mecanical energy conservation

ma.v/2 = (ma + mb).v'/2
v' = v (ma/(ma + mb))^(1/2), which is wrong

Why we can't use mecanical energy conservation, is there a energy dissipation?
Phys.Org News Partner Physics news on Phys.org
Better thermal-imaging lens from waste sulfur
Scientists observe quantum superconductor-metal transition and superconducting glass
New technique detects microscopic diabetes-related eye damage
olivermsun
olivermsun is offline
#2
Sep7-11, 09:32 PM
P: 498
Quote Quote by jaumzaum View Post
A ball A (mass ma) with initial velocity v colides with a ball B (mb) initially stopped. A and B gets the same direction/velocity v', Calculate v'
...
Why we can't use mecanical energy conservation, is there a energy dissipation?
Well, for A and B to get the same direction/velocity v' after the collision, don't they have to stick?

Does that sound like an elastic collision?


Register to reply

Related Discussions
Work,energy COM and linear momentum conservation Introductory Physics Homework 5
Linear Momentum and Conservation of Energy Question Introductory Physics Homework 14
law of conservation of linear momentum and energy Introductory Physics Homework 2
Conservation of Energy, Centre of Mass and Linear Momentum Introductory Physics Homework 7