A man holding a rifle (mass of person and rifle together is 100kg) stands on a smooth surface and fires 10 shots horizontally in 5 sec. Each bullet has a mass 10 g with a muzzle velocity of 800 ms-1. The velocity which the rifle man attains after firing 10 shots will be

Question

A man holding a rifle (mass of person and rifle together is 100kg) stands on a smooth surface and fires 10 shots horizontally in 5 sec. Each bullet has a mass 10 g with a muzzle velocity of 800 ms-1. The velocity which the rifle man attains after firing 10 shots will be (A) 8 ms-1 (B) 0.8 ms-1 (C) 0.08 ms-1 (D) -0.8 ms-1

Tardigrade Admin · Accepted Answer

According to the law of conservation of momentum,

P_{(ini t a l)} = P_{(f ina l)}

\Rightarrow m u_{1} + M u_{2} = m v_{1} + M v_{2}

\Rightarrow 0 + 0 = 10 \times 1 0^{- 3} \times 800 + [100 - 10 \times 10 \times 1 0^{- 3}] v

\Rightarrow v = \frac{- 800}{999} \Rightarrow - 0.8 m / sec

Negative sign indicates that the velocity is opposite to the direction of bullets.

Q. A man holding a rifle (mass of person and rifle together is $100 k g$ ) stands on a smooth surface and fires $10$ shots horizontally in $5$ sec. Each bullet has a mass $10 g$ with a muzzle velocity of $800 m s^{- 1}$ . The velocity which the rifle man attains after firing 10 shots will be

$8 m s^{- 1}$

$0.8 m s^{- 1}$

$0.08 m s^{- 1}$

$- 0.8 m s^{- 1}$

Q. A man holding a rifle (mass of person and rifle together is 100kg) stands on a smooth surface and fires 10 shots horizontally in 5 sec. Each bullet has a mass 10g with a muzzle velocity of 800ms−1. The velocity which the rifle man attains after firing 10 shots will be

8ms−1

0.8ms−1

0.08ms−1

−0.8ms−1

According to the law of conservation of momentum, P(inital)​=P(final)​ ⇒mu1​+Mu2​=mv1​+Mv2​ ⇒0+0=10×10−3×800+[100−10×10×10−3]v ⇒v=999−800​⇒−0.8m/sec Negative sign indicates that the velocity is opposite to the direction of bullets.

Q. A man holding a rifle (mass of person and rifle together is $100 k g$ ) stands on a smooth surface and fires $10$ shots horizontally in $5$ sec. Each bullet has a mass $10 g$ with a muzzle velocity of $800 m s^{- 1}$ . The velocity which the rifle man attains after firing 10 shots will be

$8 m s^{- 1}$

$0.8 m s^{- 1}$

$0.08 m s^{- 1}$

$- 0.8 m s^{- 1}$