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A shell of mass 200 gm is ejected from a gun of mass 4 kg by an explosion that generates 1.05 kJ of energy. The initial velocity of the shell is:

1. 100 m/s
2. 80 m/s
3. 40 m/s
4. 120 m/s

Correct answer: 100 m/s

Solution

Using the law of conservation of momentum, the initial momentum of the system is zero. After the explosion, the momentum of the shell and the gun must be equal and opposite. Let the velocity of the shell be v and the velocity of the gun be V. From energy conservation, the total kinetic energy is 1.05 kJ. Solving for v, we find it to be 100 m/s.

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