Momentum and Friction

[member 529879]

If a heavy ball is rolling on a surface, it eventually stops due to the frictional force. Where does the momentum of that ball go? Is it lost to heat, or does it maybe cause the Earth to move a very small and unnoticeable amount?

 

[Matterwave]

It causes the Earth to move a very small and unnoticeable amount. But you had to have moved the Earth a small and unnoticeable amount when you started the ball rolling so, this should just cancel that out roughly (the center of mass has shifted by a little bit in the process).

 

[member 529879]

So is momentum not lost to friction in the same way that kinetic energy is?

 

[Matterwave]

So is momentum not lost to friction in the same way that kinetic energy is?

Friction is a force and as such changes the momentum of the ball. But Newton's 3rd law says every force has an equal and opposite reaction force so that momentum is conserved. You could perhaps lose a little bit of momentum to pieces of the ground chipping or to the surrounding air or something, but you would probably just lump those elements together into "Earth".

 

[CWatters]

So is momentum not lost to friction in the same way that kinetic energy is?

No. Momentum is always conserved in any type of collision.