What happens to momentum when a car crashes into a barrier?

Question

The law of conservation of momentum states that the total momentum in a closed system is conserved.

When a car crashes into a barrier, the barrier and the car may crumple but the car will come to a stop. How exactly is the initial momentum of the car conserved?

The barrier is anchored to the Earth, so when you hit it, the Earth moves very, very slightly. — probably_someone, Mar 02 '18 at 00:10
Possible duplicate of Is momentum conserved in this situation? — Chris, Mar 02 '18 at 00:12
Remember, the car got it's momentum by "borrowing" it from Earth in the first place. — Hot Licks, Mar 02 '18 at 00:46
Related: https://physics.stackexchange.com/q/132605/25301 (and the "Linked" column on the right) — Kyle Kanos, Mar 02 '18 at 11:13

score 2 · Answer 1 · answered Mar 02 '18 at 00:53

I would answer that very differently, because momentum cannot be converted to sound, heat, or deformation. What actually happens is the same thing that would happen if a rock with the same momentum as the car hit the Earth a glancing blow and got stuck: it would change the earth's rotation and orbital velocity by an infinitesimal amount -- just enough to make sure the net angular and linear momentum do not change.

What happens to momentum when a car crashes into a barrier?

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