A railway wagon (open at the top) of mass M_{1} is moving with speed v_{1} along a straight track. As a result of rain, after some time it gets partially filled with water so that the mass of the wagon becomes M_{2} and speed becomes v_{2} Taking the rain to be falling vertically and water stationary inside the wagon, the relation between the two speeds v_{1} and v_{2} is:

1. A. v_{1}=v_{2}
2. B. \frac{1}{2}M_{1}v_{1}^{2} \lt \frac{1}{2}M_{2}v_{2}^{2}
3. C. M_{1}v_{1}=M_{2}v_{2} ✓
4. D. M_{1}v_{1} \lt M_{2}v_{2}

Correct Answer: C. M_{1}v_{1}=M_{2}v_{2}

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