Principle of conservation of momentum

[Masafi]

In a test laboratory, a car is crashed into a concrete wall and comes to rest. There is no damage to the wall. Explain of how the principle of conservation of momentum applies to this situation.

Answer:
The Earth plus car recoils with same momentum as the car had

Why "the Earth" and not just the car?

 

[dacruick]

I'm not sure I understand your question. But we assume that the concrete wall is attached indefinitely to the earth. So the Earth as a closed system must have a finite amount of momentum. All that is saying that after the collision, all the car's momentum was transferred into everything on earth . since the mass of the Earth is enormous in comparison to the car, the acceleration of the earth(and everything on it) is negligible.

 

[kerimek]

The principle of conservation of momentum states that in a closed system, the total momentum remains constant. In this situation, the car and the Earth are considered as a closed system since they are the only objects involved in the collision. This means that the total momentum of the car and the Earth before the collision is equal to the total momentum of the car and the Earth after the collision. Therefore, when the car comes to rest after crashing into the wall, the Earth must also experience a change in momentum in the opposite direction to maintain the balance of momentum in the system. This is why the Earth is included in the statement of the principle.