Question

from a rifle of mass 4kg.a bullet of mass 50gm is fired with an initial velocity of 35m/s .calculate the initial recoil velocity of the rifle?


eausure bro please help me.....​

Answer 1

$\bold{\underline{\underline{Solution\::}}}$

Given :

• Mass of rifle (m1) = 4 kg
• Mass of bullet (m2) = 50 g
• Final velocity of the bullet (v2) = 3.5 m/s

Find :

Velocity of the rifle.

According to question,

Before firing the bullet, both bullet and rifle are in the rest position.

Means, Initial velocity of both bullet and rifle is zero.

Now,

Initial Momentum = m1u1 + m2u2

Substitute the known values in above formula.

Before putting them, convert mass of bullet into kg.

So,

Mass of bullet = 0.05 kg

Now, put the values,

⇒ 4 × 0 + 0.05 × 0

⇒ 0 kg m/s

According to law of conservation of momentum,

Initial momentum = Final momentum

Means, Final momentum is also 0 kg m/s.

Let final velocity of rifle be "v1".

Final momentum = m1v1 + m2v2

⇒ 0 = (4 × v1) + (0.05 × 35)

⇒ 0 = (4 × v1) + 1.75

⇒ 4 × v1 = - 1.75

⇒ v1 = - 0.44 m/s

∴ Final velocity of the rifle is - 0.44 m/s.