Work Energy and Power - Result Question 61
64. Abombofmass $1 kg$ isthrownverticallyupwards with a speed of $100 m / s$. After 5 seconds it explodes into two fragments. One fragment of mass $400 gm$ is found to go down with a speed of $25 m / s$. What will happen to the second fragment just after the explosion? $(g=10 m / s^{2})$
[2000]
(a) It will go upward with speed $40 m / s$
(b) It will go upward with speed $100 m / s$
(c) It will go upward with speed $60 m / s$
(d) It will also go downward with speed $40 m / s$
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Answer:
Correct Answer: 64. (b)
Solution:
- (b) Speed of bomb after 5 second, $v=u-g t=100-10 \times 5=50 m / s$ Momentum of $400 g$ fragment
$=\frac{400}{1000} \times(-25)$ [downward]
Momentum of $600 g$ fragment $=\frac{600}{1000} v$
Momentum of bomb $=1 \times 50=50$
From conservation of momentum
Total momentum before splitting $=$ total momentum after splitting.
$\Rightarrow 50=-\frac{400}{1000} \times 25+\frac{600}{1000} v$
$\Rightarrow v=100 m / s \quad$ [upward]
