Question

A $3kg$ sphere makes an inelastic collision with another sphere at rest and they stick together after collision. After collision, the composite mass move with a speed of ${\left(\frac{1}{4}\right)}^{th}$ of the initial velocity of $3kg$ sphere. The mass of second sphere is:

• A. $12kg$
• B. $9kg$
• C. $6kg$
• D. $3kg$

Answer 1

Answer: (B)

$9kg$

Since there is no external force acting on the system, momentum must remain conserved. Let the mass of second sphere be $m$.

Hence, $3v=(3+m)\frac{v}{4}$

Thus, $m=9kg$