Particle A (60kg) moves right at 50m/s. It collides with particle B (250kg) moving left at 10m/s. If after the collision particle A moves left at 20m/s, calculate the final velocity of particle B

First the total initial momentum of the particle system is calculated. Treat right as the positive x-direction and left as the negative x-direction. Then:Total initial momentum (Pi) = Inital momentum of A + Intital momentum of BPi = (60kg)(+50ms^-1) + (250kg)(-10ms^-1) = (3000kg ms^-1) + (-2500kg ms^-1) = +500kg ms^-1Conservation of momentum:Total inital momentum (Pi) = Total final momentum (Pf)Pf = (60kg)(-20ms^-1) + (250kg)(vB) = (-1200kgms^-1) + (250kg vB) =500kgms^-1where vB is the unknown final velocity of particle B.Rearranging the above to make vB the subject:vB = ( 500kgms^-1 - -1200kgms^-1)/(250kg) = (1700kgms^-1)/(250kg) = 6.8ms^-1