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# From a rifle of mass 4 kg, a bullet of mass 50 g is fired with an initial velocity of 35 m s^(−1). Calculate the initial recoil velocity of the rifle. - CBSE Class 9 - Science

ConceptConservation of Momentum

#### Question

From a rifle of mass 4 kg, a bullet of mass 50 g is fired with an initial velocity of 35 m s−1. Calculate the initial recoil velocity of the rifle.

#### Solution

Mass of the rifle, m1 = 4kg

Mass of the bullet, m2 = 50g = 0.05 kg

Recoil velocity of the rifle = v1

Bullet is fired with an initial velocity, v2 = 35 m/s

Initially, the rifle is at rest.

Thus, its initial velocity, v = 0

Total initial momentum of the rifle and bullet system (m1 + m2)v = 0

Total momentum of the rifle and bullet system after firing:-

= m1v1 + m2v2 = 4(v1) + 0.05 x 35 = 4v1 + 1.75

According to the law of conservation of momentum:

Total momentum after the firing = Total momentum before the firing

4v1 + 1.75 =0

v_1 = 1.75/4 =-0.4375" m/s"

The negative sign indicates that the rifle recoils backwards with a velocity of 0.4375 m/s.

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#### APPEARS IN

NCERT Solution for Science Textbook for Class 9 (2018 to Current)
Chapter 9: Force and Laws of Motion
Q: 3 | Page no. 126

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Solution From a rifle of mass 4 kg, a bullet of mass 50 g is fired with an initial velocity of 35 m s^(−1). Calculate the initial recoil velocity of the rifle. Concept: Conservation of Momentum.
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