Conservation of momentum of ball thrown

[merry]

If say, a object such as a ball with velocity v m/s and mass m kg collides with a stationary solid wall, and the ball rebounds back with a velocity of v' m/s while the wall remains stationary, is momentum conserved?

Since the wall is stationary, I would assume that the initial and the final momenta of the wall are zero. Hence applying the law of conservation of momentum,
p initial = p final
mv=mv'

But then the velocity of the ball is in the opposite direction after the impact, so how would I justify the conservation of momentum in this case?
Also, would the collision be elastic? (assuming the wall does not deform)
Thanks!

 

[xxChrisxx]

No the collision is partially inelastic at has to be as the COR isn't 1, in all collisions the momentum is conserved. As the wall is very large it doesn't appear to move (it also only moves locally, by deformation).

 

[tiny-tim]

If say, a object such as a ball with velocity v m/s and mass m kg collides with a stationary solid wall, and the ball rebounds back with a velocity of v' m/s while the wall remains stationary, is momentum conserved?

Hi merry!

By good ol' Newton's second law , total momentum in a direction is only conserved if there is no external force in that direction.

So collisions in space, or collisions on a frictionless surface (where the only external forces are normal to the motion), obey conservation of momentum,

but your wall has (I assume ) a horizontal force keeping it in place, so horizontal momentum is not conserved.

 

[merry]

Hi merry!

By good ol' Newton's second law , total momentum in a direction is only conserved if there is no external force in that direction.

So collisions in space, or collisions on a frictionless surface (where the only external forces are normal to the motion), obey conservation of momentum,

but your wall has (I assume ) a horizontal force keeping it in place, so horizontal momentum is not conserved.

Hehe XD that makes sense! Thank you! =D

 

[diazona]

Of course, if you consider the momentum of whatever is holding the wall in place, momentum would be conserved. So if you could somehow measure the momentum of the wall, the Earth, etc. very precisely, you should find that the total momentum is conserved. (Actually, even then there are external forces, like gravity... but if there weren't, then you should find that the total momentum would be conserved ;-)

 

[merry]

Of course, if you consider the momentum of whatever is holding the wall in place, momentum would be conserved. So if you could somehow measure the momentum of the wall, the Earth, etc. very precisely, you should find that the total momentum is conserved. (Actually, even then there are external forces, like gravity... but if there weren't, then you should find that the total momentum would be conserved ;-)

That is an interesting idea Thank you =D