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Concepts Of Physics MCQ Edition [Volume 1]PhysicsCentre of Mass, Linear momentum, Collision

A block travelling in the air breaks into two parts, and these parts separate. Which of the following must be true for the system?

Options

  1. AThe total kinetic energy must change.
  2. BThe total kinetic energy must be conserved.
  3. CThe total momentum must be conserved.
  4. DThe total momentum must change.

Correct answer

D. The total momentum must change.

Step-by-step solution

When a block is travelling in the air, it is continuously acted upon by the external force of gravity (and potentially air resistance). According to Newton's second law, the rate of change of momentum is equal to the net external force. Since the net external force on the system is non-zero, the total momentum of the system is not conserved and must change over time. When the block breaks into two parts and they separate, the internal forces of the system do positive work. This process converts internal energy (suc

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