Question

There are two balls A and B of mass $1\text{kg}$ and $2\text{kg}$ respectively. Ball A is moving with a velocity of $2\text{m/s}$ and collides with B at rest. After the collision, A comes to rest and B starts moving. Find the velocity of B.

• A. $1\text{m/s}$
• B. $2\text{m/s}$
• C. $3\text{m/s}$
• D. $4\text{m/s}$

Answer 1

The correct option is A $1\text{m/s}$

We know,
Initial momentum, ${\text{P}}_1=(\text{m}\times \text{u})+(\text{M}\times \text{U})$
Final momentum, ${\text{P}}_2=(\text{m}\times \text{v})+(\text{M}\times \text{V})$

From the law of conservation of momentum,${\text{P}}_1={\text{P}}_2$
$(\text{m}\times \text{u})+(\text{M}\times \text{U})=$$(\text{m}\times \text{v})+(\text{M}\times \text{V})$
$⟹$
$(1\times 2)+(2\times 0)=(1\times 0)+(2\times \text{V})$
$\text{V}=1\text{m/s}$

Therefore, the final velocity of ball B will be $1\text{m/s}$.