Question

a bullet 8g fired from a rifle of mass 8kg moves with velocity of 400m/s .find recoil velocity of rifle .​

Answer 1

Momentum conservation:

• As the bullet fired is the result of internal firces inside the gun.
• No external force during the process.

$\implies\rm \vec{F_{ext}} = 0$

$\implies\rm \dfrac{dp}{dt} = 0$

★ Momentum remain conserved.

Initial Momentum = Final Momentum

• 0 = mv + MV

$\to\rm V = \dfrac{-mv}{M}$

$\to\rm V = \dfrac{-8\times 10^{-3} \times 400}{8}$

$\to\bf V = 0.4\: (\hat{-i} )\: ms^{-1}$

★ So, recoil velocity of rifle is 0.4 m/s opposite to the direction of bullet.

Answer 2

Explanation:

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Momentum conservation:

As the bullet fired is the result of internal firces inside the gun.

No external force during the process.

$\implies\rm \vec{F_{ext}} = 0$

$\implies\rm \dfrac{dp}{dt} = 0$

★ Momentum remain conserved.

Initial Momentum = Final Momentum

0 = mv + MV

$\to\rm V = \dfrac{-mv}{M}$

$\to\rm V = \dfrac{-8\times 10^{-3} \times 400}{8}$

$\to\bf V = 0.4\: (\hat{-i} )\: ms^{-1}$

★ So, recoil velocity of rifle is 0.4 m/s opposite to the direction of bullet.

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