Question

3. From a rifle of mass 4 kg, a bullet
of mass 50 g is fired with an
initial velocity of 35 ms
Calculate the initial recoil velocity
of the rifle.​

Answer 1

Explanation:

conservation of momentum .

momentum of bullet = momentum of gun

4×recoil velocity = 0.050×35

recoil velocity = 0.44 m/s

Answer 2

Mass of rifle (M) = 4 kg

Mass of bullet (m) = 50 g = 0.05 kg

Velocity of rifle (v) = 35 m/s

Recoil velocity of rifle (V) = V m/s

★ Apply Conservation of momentum ,

It states that initial momentum of the system is equals to final momentum .

Initial momentum = ( M + m ) u

• Initially , system is in rest

⇒ Initial momentum = ( M + m ) 0

⇒ Initial momentum = 0 Kg-m/s

This momentum is equals to final momentum , a/c to the conservation of momentum .

➠ 0 = MV + mv

➠ 0 = (4)V + (0.05)(35)

➠ 4V = - 1.75

➠ V = - 0.4375 m/s

Note : - ve sign of recoil velocity of rifle denotes opposite direction to the motion of velocity of bullet