Question

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

Answer 1

Given :

Mass of rifle = 4kg

Mass of bullet = 50g = 0.05kg

Initial velocity of bullet = 35m/s

To Find :

Recoil velocity of the rifle.

Solution :

❒ Since no external force acts on the whole system, linear momentum of system is conserved.

• We know that momentum is measured as the product of mass and velocity.

Initially, both rifle and bullet are at rest position hence Initial momentum of the system will be zero$.$

➙ 0 = mv + MV

» m denotes mass of bullet

» v denotes velocity of bullet

» M denotes mass of rifle

» V denotes recoil velocity of rifle

By substituting the given values;

➙ 0 = (0.05)(35) + 4V

➙ 4V = -1.75

➙ V = -1.75/4

➙ V = -0.44 m/s

[Note : Negative sign shows opposite direction.]

Answer 2

Given :

Mass of rifle = 4kg

Mass of bullet = 50g = 0.05kg

Initial velocity of bullet = 35m/s

To Find :

Recoil velocity of the rifle.

Solution :

❒ Since no external force acts on the whole system, linear momentum of system is conserved.

We know that momentum is measured as the product of mass and velocity.

Initially, both rifle and bullet are at rest position hence Initial momentum of the system will be zero$.$

➙ 0 = mv + MV

» m denotes mass of bullet

» v denotes velocity of bullet

» M denotes mass of rifle

» V denotes recoil velocity of rifle

By substituting the given values;

➙ 0 = (0.05)(35) + 4V

➙ 4V = -1.75

➙ V = -1.75/4

➙ V = -0.44 m/s

[Note : Negative sign shows opposite direction.]