Question

Refer to two 1 kg masses moving toward each other, one mass with velocity $v_1$= 10 m/s, the other with velocity $v_2$= 20 m/s. What is the velocity of the center of mass?

• A. 0 m/s
• B. 5 m/s to the left
• C. 10 m/s to the left
• D. 15 m/s to the left
• E. 20 m/s to the left

Answer 1

The correct option is B 5 m/s to the left

Using law of conservation of momentum,

$Initialmomentum=Finalmomentum{m}_1{v}_1+m_2{v}_2=(m_1+m_2)v10\times 1-20\times 1=(1+1)vv=-\frac{10}{2}m/sv=5m/stowardsleft$