Question

A ball of mass $m$ falls vertically from a height $h$ and collides with a block of equal mass $m$ moving horizontally with a velocity $v$ on a surface. The coefficient of kinetic friction between the block and the surface is ${\mu }_k=0.2$, while the coefficient of resittution ($e$) between the ball and the block is $0.5$. There is no friction acting between the ball and the block. The velocity of the block just after the collision decreases by

• A. can't be said
• B. $0$
• C. $0.1\sqrt{2gh}$
• D. $0.3\sqrt{2gh}$

Answer 1

The correct option is A can't be said

By using change in impulse formula

$\Delta p=F\Delta t$

$=\frac{3}{2}m\sqrt{2gh}$

where as on black

$\mu F\Delta t=mv-m{v}^1$

$0.2\times \frac{3}{2}\sqrt{2gh}\times m=m(v-v^1)$

$\therefore (v-v^1)=0.3\sqrt{2gh}$