Question

a car 'A' of mass 1500 kg,travelling at 25m/s collides with another car 'B' of mass 1000 kgtravelling at 40m/s in the same direction.after collision,velocity of car 'A'becomes 20 m/s.find velocity of car 'B' after collision?

Answer 1

Before Collision:

Car A:
m (mass) = 1500 kg
​u (initial velocity) = 25m/s

Car B:
m (mass) = 1000kg 
​u (initial velocity) = 15m/s
 
After Collision:

According to law of conservation of momentum-
Total momentum before collision = Total momentum after collision

m1u1 + m2u2 = m1v1 + m2v21500 X 25 + 1000 X 15 = 1500 X 20 + 1000 X v237,500 +  15,000 = 30,000 + 1000 X v252,500 = 30,000 + 1000 X v252,500 - 30,000 = 1000 X v222500 = 1000 X v222500 / 1000 = v222.5 = v2Therefore, the velocity after collision = 22.5 m/s