# Law of conservation of momentum?

2
by prettha

2015-10-11T18:38:34+05:30
The sum of momentum of two objects before collision and sum of momentum of two objects after collision are equal.

let A and B be any objects
initial velocity of A =u1
initial velocity of B = u2
let mass of A be m1
let mass of B e m2
let both the objects collide after some time and collision lasts for t seconds
let the velocity of A after collision =v1
let the velocity of B after collision =v2
momentum =mass *velocity
momentum of A before collision =m1*u1
momentum of B before collision = m2*u2
momentum of A after collision = m1*v1
momentum of B after collision = m2*v2
now we know the rate of change of momentum  =mass *rate of  change in velocity =mass*change in velocity /time
rate of  change of momentum of A during collision ,FAB =m1(v1-u1)/t
rate of change of momentum of B during collision, FBA  =m2 (v2-u2)/t
FAB= -FBA
m1(v1-u1)/t = -m2 (v2 -u2)/t
m1(v1-u1) = -m2(v2-u2)
m1v1-m1u1 = -m2v2+m2u2
m1v1+m2v2 = m1u1+m2u2
m1u1+m2u2 = m1v1+m2v2