Question

A 10gm bullet moving directly upward at 1000 m/s strikes and passes through the center of mass of a 10 kg block initially at rest .The bullet emerges from the block moving directly upward at 400 m/s. What will be velocity of the block just after the bullet comes out of it ?

• A. 0.6 m/s
• B. 1 m/s
• C. 0.4 m/s
• D. 1.4 m/s

Answer 1

Answer: (A)

Given,
Weight of bullet $\left(m_B\right)=10gm$
$=10\times 10^{-3}kg$
Weight of block $(M)=10kg$
Initial velocity of bullet $\left(v_i\right)=1000m/s$
Final velocity of bullet $\left(v_f\right)=400m/s$
By the law of conservation of momentum,
$m_B{V}_i=m_B{V}_f+10V$
[where, $v=$ velocity of block]
$\left(10\times 10^{-3}\right)(1000)=\left(10\times 10^{-3}\right)(400)+10v$
$10=4+10V$
$10V=10-4$
$V=\frac{6}{10}=0.6m/s$