question_answer 11)

Two objects, each of mass 1.5 kg, are moving in the same straight line but in opposite directions. The velocity of each object is 2.5 m s–1 before the collision during which they stick together. What will be the velocity of the combined object after collision?

Answer:

Let the two objects are A and B. Mass of object A, m1 = 1.5 kg Mass of object B, m2 = 1.5 kg Velocity of object A before collision, u1 = 2.5 m s-1 Velocity of object B before collision, u2 = -2.5 m s-1 Total momentum of object A and B before collision m1u1 + m2u2 = 1.5 x 2.5 - 1.5 x 2.5 = 0 Mass of combined object after collision = (m1 + m2) = 3.0 kg Let, velocity of combined object after collision = V m s-1 Total momentum of combined object after collision = (m1 + m2) V = (3V) kg m s-1 According to the law of conservation of momentum Momentum after collision = Momentum before collision i.e.          3 V = 0 or V = 0