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Principle of conservation of momentum

  • Thread starter Masafi
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  • #1
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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?
 

Answers and Replies

  • #2
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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 transfered 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.
 

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