Question

A bullet of mass 10 g is fired from a gun of mass 750 g. Find the velocity of the gun if the bullet moves with a speed of 100 m/s.

Answer 1

Answer:

https://www.toppr.com/ask/en-in/question/a-bullet-of-mass-100-g-is-fired-from-a-gun-of-mass-20-kg/

Explanation:

Mass of bullet, m=100g=

1000

100

kg=

10

1

kg

Velocity of bullet, v=100ms

−1

Mass of gun, M=20kg

Let recoil velocity of gun =V

Before firing, the system (gun+bullet) is at rest, therefore, initial momentum of the system =0

Final momentum of the system = momentum of bullet + momentum of gun

=mv+MV=

10

1

×100+20V=10+20V

Applying law of conservation of momentum, Final momentum = Initial momentum

i.e., 10+20V=0

20V=−10

or V=−

20

10

=−0.5ms

−1

.

Negative sign shows that the direction of recoil velocity of the gun is opposite to the direction of the velocity of the bullet.

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Answer 2

Answer:

1.3333333....... m/s

Explanation:

Law Of Conservation Of Momentum - m1u1 + m2u2 = m1v1 + m2v2

hence m1 = 10 gram = 0.01 kg

m2 = 750 g = 0.75 Kg

Before Firing the velocity of bullet - u = 0

Now m1u1 + m2u2 = m1v1 + m2v2

So , ( 0.01 * 0 ) + ( 0.75 * 0 ) = ( m1 + m2 ) v

so 0 = ( m1 + m2) v

hence -  ( 0.01 * 100 ) + ( 0.75 ) v = 0

1 + 0.75v2 = 0

0.75v2 = -1

v2 = -1 / - 0.75

v2 = 1.333333...... m/s