Page No 127: - Chapter 9 - Force & Laws Of Motion - Ncert Solutions class 9 - Science

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Question 4:

Two objects of masses 100 g and 200 g are moving along the same line and direction with velocities of 2 m s⁻¹ and 1 m s⁻¹, respectively. They collide and after the collision, the first object moves at a velocity of 1.67 m s⁻¹. Determine the velocity of the second object.

Answer:

Mass of one of the objects, m₁ = 100 g = 0.1 kg

Mass of the other object, m₂ = 200 g = 0.2 kg

Velocity of m₁ before collision,  m/s

Velocity of m₂ before collision,  m/s

Velocity of m₁ after collision, 

Velocity of m₂ after collision = 

According to the law of conservation of momentum:

Total momentum before collision = Total momentum after collision

Hence, the velocity of the second object becomes 1.165 m/s after the collision.