Question

Two bodies of masses $3\text{kg}$ and $5\text{kg}$ are moving with velocities $25\text{m/s}$ and $15\text{m/s}$ towards each other due to mutual force of attraction as shown in the figure. What is the velocity of their center of mass?

• A. $0\text{m/s}$
• B. $15\text{m/s}$
• C. $10\text{m/s}$
• D. $22\text{m/s}$

Answer 1

The correct option is A $0\text{m/s}$

Given : $m_1=3\text{kg}$
$m_2=5\text{kg}$
$v_1=25\text{m/s}$
$v_2=-15\text{m/s}$
${\overrightarrow{v}}_{com}=\frac{m_1{v}_1+m_2{v}_2}{m_1+m_2}=\frac{3\times 25+5\times (-15)}{3+5}$
= $\frac{75-75}{8}\text{m/s}$
$=0\text{m/s}$