Question

A spacecraft of mass $100\,kg$ breaks into two when its velocity is $10^4\,ms^{-1}$ . After the break, a mass of $10\, kg$ of the space craft is left stationary. The velocity of the remaining part is

• A. $10^3\, m\,s^{-1}$
• B. $11.11 \times 10^3\, m\,s^{-1}$
• C. $11.11 \times 10^2 \,m\,s^{-1}$
• D. $10^4\, ms^{-1}$
• E. $1100\, ms^{-1}$

Answer 1

Answer: (B)

Given, $m=100\, kg , m_{2}=10 \,kg$ and $u=10^{4} \,ms ^{-1}$
From conservation of momentum,
$m \cdot u =m_{1} v_{1}+m_{2} v_{2}$
$100 \times 10^{4} =20 \times 0+90 \times v_{2} $
$100 \times 10^{4} =0+90 \times v_{2} $
$v_{2} =\frac{100 \times 10^{4}}{90} $
$v_{2} =1.1 \times 10^{4} $
$v_{2} =11.11 \times 10^{3} \,ms ^{-1}$