Question

A body of mass 20 kg is moving with a velocity of 2v and another body of mass 10 kg moving with velocity v along same direction. The velocity of their centre of mass is:

• A. 5 v/3
• B. 2 v/3
• C. v
• D. Zero

Answer 1

Answer: (A)

5 v/3

Answer 2

Velocity of centre of mass

${\overset{\rightarrow}{v}}_{cm} = \frac{m_{1}{\overset{\rightarrow}{v}}_{1} + m_{2}{\overset{\rightarrow}{v}}_{2}}{m_{1} + m_{2}} = \frac{20 \times 2v + 10 \times v}{30} = \frac{5}{3}v$