Question

Two bodies are accelerating towards each other. After sometime they collide. Which one of the following statements is true about the system?

• A. The total momentum remains conserved about the center of mass
• B. The total momentum does not remain conserved.
• C. The total momentum remains conserved during collision
• D. The total momentum remains conserved

Answer 1

Answer: (C)

The total momentum remains conserved during collision

Answer 2

The total momentum of a system is conserved if no net external force acts on it. When two bodies collide, the internal forces between them are very large and act for a very short duration. These impulsive internal forces are much greater than any external forces that might be acting on the system. Therefore, during the brief period of collision, the net external impulse is negligible, and the total momentum of the system (sum of momenta of the two bodies) just before and just after the collision remains conserved. This principle holds true regardless of whether external forces were present before or after the collision causing the initial acceleration.

Key Concepts:

• Conservation of Momentum: The total momentum of a closed system remains constant if no external forces act on it.
• Impulsive Forces: Large forces acting for a short duration, common in collisions.
• External vs. Internal Forces: External forces can change the momentum of a system, while internal forces within the system do not.

During the collision, internal impulsive forces dominate, making the conservation of momentum a valid approximation regardless of external forces that might be present before or after the collision.