Question

a heavy car a of mass 2000 kg travelling at 10 metre per second and has a head - on collision with a sports car B of mass 500 kg .if both cause of dead on colliding ,what was the velocity of cars b?

Answer 1

By momentum balance, 

0 = 2000 * 10 + 500 * v 

v = - 40 m/s 

Velocity of B is 40 m/s in a direction opposite to the velocity of A.

Answer 2

Applying conservation of momentum,

P1= P2

Mass of car A be 2000 kg

Mass of car B be 500 kg

velocity of car A before impact = Va= 10 m/s

Velocity of car B before impact = Vb= ?

Velocity of car A after impact= 0

Velocity of car B after impact = 0

2000 Va +500 Vb = 2000 (0) + 500 (0)

2000 x 10+ 500 Vb=0

Vb= -2000/500 = - 40 m/s

-ve sign shows that Va and Vb are opposite in direction.