Question

A mass of $1 \,kg$ is thrown up with a velocity of $100 \,m / s$. After $5$ seconds, it explodes into two parts. One part of mass $400 \,g$ comes down with a velocity $25 \,m / s$. The velocity of other part is (Take $g =10 \,ms ^{-2}$ )

• A. $40\, m / s \uparrow$
• B. $40 \,m / s \downarrow$
• C. $100 \,m / s \uparrow$
• D. $60 \,m / s \uparrow$

Answer 1

Answer: (C)

Velocity after $5 \sec , v = u - gt$
$=100-10 \times 5=50 \,m / s$
By conservation of momentum
$1 \times 50=0.4 \times(-25)+0.6 \times v^{\prime}$ $60=0.6 \times v^{\prime} $
$\Rightarrow v^{\prime}=100 m / s$ upwards