Question

A bullet of mass 20 grams moving with a velocity of $100m{s}^{-1}$ strikes a wooden block of mass 80 grams and gets embedded into it. What is the velocity acquired by the block?

• A. 10 $m{s}^{-1}$
• B. 30 $m{s}^{-1}$
• C. 20 $m{s}^{-1}$
• D. 50 $m{s}^{-1}$

Answer 1

The correct option is C

20 $m{s}^{-1}$

Here, mass of bullet ($m_1$) = 20 g = 0.02 kg, velocity of bullet ($v_1$) = $100m{s}^{-1}$, mass of wooden block = 80 g = 0.08 kg.

Momentum of the bullet = $m_1\times v_1$ = $0.02\times 100$ kg $m{s}^{-1}$

Mass of wooden block along with embedded bullet ($m_2$) = 0.02 + 0.08 = 0.10 kg

Velocity of wooden block + bullet = $v_2$

By applying law of conservation of momentum,

$m_1\times v_1$ = $m_2\times v_2$

$0.02\times 100$ = $0.10\times v_2$

$\Rightarrow$$v_2$ = $\frac{0.02\times 100}{0.10}$ = 20 $m{s}^{-1}$