Work Energy and Power - Result Question 15

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17. A person holding a rifle (mass of person and rifle together is $100 kg$ ) stands on a smooth surface and fires 10 shots horizontally, in $5 s$. Each bullet has a mass of $10 g$ with a muzzle velocity of $800 ms^{-1}$. The final velocity acquired by the person and the average force exerted on the person are [NEET Kar. 2013]

======= ####17. A person holding a rifle (mass of person and rifle together is $100 kg$ ) stands on a smooth surface and fires 10 shots horizontally, in $5 s$. Each bullet has a mass of $10 g$ with a muzzle velocity of $800 ms^{-1}$. The final velocity acquired by the person and the average force exerted on the person are [NEET Kar. 2013]

3e0f7ab6f6a50373c3f2dbda6ca2533482a77bed:content/english/neet-pyq-chapterwise/physics/work-energy-and-power/work-energy-and-power—result-question-15.md (a) $-1.6 ms^{-1} ; 8 N$

(b) $-0.08 ms^{-1} ; 16 N$

(c) $-0.8 ms^{-1} ; 8 N$

(d) $-1.6 ms^{-1} ; 16 N$

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Answer:

Correct Answer: 17. (c)

Solution:

  1. (c) According to law of conservation of momentum

$MV+mnv=0$

$\Rightarrow V=\frac{-m N v}{M}=\frac{-0.01 kg \times 10 \times 800 m / s}{100}$

$\Rightarrow-0.8 m / s$

According to work energy theorem,

Average work done $=$ Change in average

kinetic energy

i.e., $F _{av} \times S _{av}=\frac{1}{2} m V_ms^{2}$

$\Rightarrow \frac{F _{av} V _{\max } t}{2}=\frac{1}{2} m \frac{V _{\text{rms }}^{2}}{2}$

$\Rightarrow F _{av}=8 N$