Question

from a rifle of mass5kg a bullet of mass 50
grams is fired with an initial velocity of 50m/s.
calculate the initial recoil velocity of the rifle​

Answer 1

$\sf \: - 0.5m/s$

GiVen:-

• Mass of rifle (M) = 5Kg

• Final velocity of rifle (V) = 0

• Mass of bullet (m) = 50gm = 0.05kg

• Initial velocity of bullet (u) = 50 m/s

• Final velocity of bullet (v) = 0

To Find:-

• We have to find initial recoil velocity of rifle (U).

AnSwer:-

★ Initial momentum = final momentum

(As external force act on system = 0 , linear momentum of system remains constant.)

★ By using Law of Conservation of Momentum,

$\implies\sf \: \: 0.05 \times 50 + 5 \times U = m \times 0 + M \times 0 \\ \\ \implies\sf \: \:0.05 \times 50 + 5U = 0 \\ \\ \implies\sf \: \:5U = -0.05\times50 \\ \\ \implies\: \: { \underline{ \boxed{ \sf{ \purple{U = -0.5 m/s}}}}}$

Negative sign represents that the velocity of rifle is just opposite to the bullet and hence we can say it as recoil velocity.

Therefore, initial velocity of refile is -0.5 m/s