Rankers Physics
Topic: Center of Mass , Momentum and Collision
Subtopic: Motion of Center of Mass

A boat of mass 40 kg is at rest. A dog of mass 4 kg starts moving in the boat with velocity of 10 m/s. What is the speed of boat ?
1 m/s
2 m/s
4 m/s
8 m/s

Solution:

\[ v_{cm}=\frac{(m_{1}v_{1}+ m_{2}v_{2})}{(m_{1}+m_{2})} \]

As Center of mass will remain at rest  \[ (m_{1}v_{1}+ m_{2}v_{2}) = 0 \]

4 × 10 + 40 × v = 0

v = -1 m/s

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