Question

A body of mass $10\, kg$ moving with velocity $10\, m/s$ collides with a stationary body of mass $5\, kg$. After collision both bodies stick to each other, velocity of the joint body after collision is:

• A. $ \frac{3}{10}\,m/s $
• B. $ 20\,m/s $
• C. $ \frac{20}{3}\,m/s $
• D. $ 15\,m/s $

Answer 1

Answer: (C)

In an inelastic collision, linear momentum is conserved.
Since, in given collision the two bodies stick to each other, so collision is inelastic.
Applying conservation of linear momentum.
$m_{1} v_{1}+m_{2} v_{2}=\left(m_{1}+m_{2}\right) v $ ..(i)
where $v$ is the velocity of joint body.
Given, $m_{1}=10 \,kg , v_{1}=10 \,m / s , m_{2}=5 \,kg$,
$v_{2}=0$. Substituting the values in Eq. (i), we get
$10 \times 10+5 \times 0=(10+5) v$
or $100=15\, v$
or $v=\frac{100}{15}=\frac{20}{3} m / s$