Question

A steel ball having mass $100\text{g}$ is moving with velocity $20\text{m/s}$. In the same direction, a ball of clay having mass $20\text{g}$ is moving with velocity $10\text{m/s}$. If after some time, both balls collide and stick together, what will be the speed of steel ball after collision?

• A. $1.833\text{m/s}$
• B. $18.33\text{m/s}$
• C. $11.33\text{m/s}$
• D. $16.66\text{m/s}$

Answer 1

The correct option is B $18.33\text{m/s}$

Let $m_1$ and $u_1$ denotes the mass and initial velocity of steel ball and $m_2$ and $u_2$ denotes the mass and initial velocity of clay ball.
Before collision

After collision,

After collision, both balls stick together. Therefore it is perfectly inelastic collision.
Applying conservation of momentum before and after collision.
$m_1{u}_1+m_2{u}_2=(m_1+m_2)v$
$0.100\times 20+\left(0.020\right)\times \left(10\right)=(0.100+0.020)\times v$
$v=18.33\text{m/s}$