Question

A small block of mass $2\text{kg}$ having a velocity of $50\text{m/s}$ hits a larger block of mass $10\text{kg}$ initially at rest. The collision is perfectly inelastic and the smaller block sticks to the larger block. Find the velocity of the combined mass after the collision.

• A. $8.33\text{m/s}$
• B. $16.66\text{m/s}$
• C. $33.33\text{m/s}$
• D. $21\text{m/s}$

Answer 1

The correct option is A $8.33\text{m/s}$

Before collision
Initially larger block is at rest. Therefore $u_2=0$

After collision

Applying P.C.L.M before and after collision.
$m_1{u}_1+m_2{u}_2=(m_1+m_2)v$
$2\times 50+10\times 0=(2+10)v$
$\frac{100}{12}=v$
$v=8.33\text{m/s}$
$\therefore$ Velocity of combined mass after collision is $8.33\text{m/s}$
Hence the correct option is (a).