Question

Law of conservation of momentum 

Answer 1

The total linear momentum of an isolated system remains constant of changes within system

Answer 2

Momentum

Momentum is the product of mass and velocity of an object.

Momentum is a vector quantity.

Suppose an object A has mass 'm1' and it's initial velocity is 'u1'.

An object B has mass 'm2' and it's initial velocity as 'u2'.

According to the formula for momentum, the

initial momentum of A is "m1 u1" and that of B is "m2u2".

Suppose these objects collide.

Let the force on A due to B be F1.

This force will cause acceleration in A and it's velocity will become "v1".

Momentum of A after collision = "m1v1"

According to Newton's third law of motion, 'A'

also exerts force in 'B' but in the opposite direction. This will cause a change in the momentum of "B".

It its velocity after collision is v2,

The Momentum of B after collision= m2v2.

If F2 is the force that acts on object B,

F2 = - F1

Therefore,

m2 a2 = - m1 a1 .... {F = ma}

Hence, after derivation, we get,

(m2 v2 + m1 v1) = (m1 u1 + m2 u2)

The magnitude of total final momentum =

The magnitude of total initial momentum.

When two external force acts on two interacting objects , their total momentum remains constant. It does not change.

When two objects collide,the total momentum before collision = Total momentum after collision.