Question

(2
03. From a rifle of mass 4 kg, a bullet of mass 50 is fired with an initial velocity of 35 m st. Calculate
the initial recoil velocity of the rifle.​

Answer 1

Ans. -0.4375 m/s

REFER ATTACHMENTS

GIVEN

Mass of the rifle = M1 = 40 kg

Mass of the bullet = M2 = 50 gm

50 gm = 50/1000 = 0.05 kg

Velocity of the bullet = V2 = 35m/s

Let, the recoil velocity of rifle = V1

☆ Initially, rifle and bullet are at rest, so the momentum will be zero (cuz velocity is 0)

TO FIND

Recoil velocity of the gun

CALCULATIONS

Already said, but here's the calcution

⇨ Total momentum before firing

= ( M1 + M2 ) × V

= ( 4 + 0.05 ) × 0

= 4.05 × 0

= 0 kg m/s

⇨ Total momentum after firing

= ( M1 × V1 ) + ( M2 × V2 )

= ( 4 × V1 ) + ( 0.05 × 35 )

= 4V1 + 1.75

According to law of conservation of momentum,

Momentum after firing = Momentum before firing

4V1 + 1.75 = 0

4V1 = 0 - 1.75 = -1.75

V1 = -1.75 ÷ 4 = -175 ÷ 400 = -0.4375

SOLUTION

Recoil velocity of rifle after firing = -0.4375 m/s

Minus (-) sign indicates that it's a recoil velocity [a backward motion]

HOPE, IT HELPS YOU

KEEP SMILING :D

Are u studying in 9 grade :)