Question

A bullet weighing $10g$ and moving at $300m/s$ strikes a $5kg$ ice and drops dead. The ice block is sitting on a frictionless level surface. The speed of the block after the collision, is

• A. $6cm/s$
  
• B. $6m/s$
  
• C. $60cm/s$
  
• D. $60m/s$
  

Answer 1

The correct option is A $6cm/s$

Mass of bullet $m=10g=0.01kg$ and its initial velocity $v=300m/s$

Mass of ice block $M=5kg$

Initial speed of block $v=0m/s$

Initially, momentum of the system $p_i=mu+Mv=\left(0.01\right)\left(300\right)+0=3kgm/s$

Let the speed of the bullet+ block system after the collision be $V$.

Finally, momentum of the system $p_f=(m+M)V=(0.01+5)V\approx 5V$

Using conservation of linear momentum : $p_f=p_i$

$\therefore$ $5V=3$

$⟹V=0.6m/s=6cm/s$