Conservation of momentum in collisions
Consider a system of two particles A and B. Let the momentum of the particles before collision is and respectively and after collision let the momentum are and respectively. Let the particles are in contact for a small time Δt during collision.
Using Newton’s second law, force on A due to B :
Similarly, force on B due to A,
From Newton’s third law,
∴ From equations (1) and (2),
⇒ Total linear momentum of the system before collision = Total linear momentum of the system after collision