Principle of conservation of momentum

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SUMMARY

The principle of conservation of momentum states that in a closed system, the total momentum before an event must equal the total momentum after the event. In the discussed scenario, when a car crashes into a concrete wall, the momentum of the car is transferred to the Earth, which is considered part of the closed system. Since the mass of the Earth is significantly larger than that of the car, the resulting acceleration of the Earth is negligible, allowing the momentum to be conserved without observable effects on the wall or the Earth.

PREREQUISITES
  • Understanding of basic physics concepts, particularly momentum
  • Familiarity with closed systems in physics
  • Knowledge of mass and acceleration relationships
  • Basic principles of collision dynamics
NEXT STEPS
  • Study the mathematical formulation of momentum conservation in physics
  • Explore real-world applications of momentum conservation in vehicle collisions
  • Learn about closed systems and their implications in physics
  • Investigate the relationship between mass, force, and acceleration in Newtonian mechanics
USEFUL FOR

Students of physics, educators teaching momentum concepts, and professionals in automotive safety engineering will benefit from this discussion.

Masafi
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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?
 
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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 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.
 

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