Mass of one of the objects, m_{1 }= 100 g = 0.1 kg

Mass of the other object, m_{2} = 200 g = 0.2 kg

Velocity of m_{1} before collision, v_{1} = 2 m/s

Velocity of m_{2} before collision, v_{2} = 1 m/s

Velocity of m_{1} after collision, v_{3} = 1.67 m/s

Velocity of m_{2} after collision = v_{4}

According to the law of conservation of momentum:

Total momentum before collision = Total momentum after collision

m_{1}v_{1 }+ m_{2}v_{2} = m_{1}v_{3} + m_{2}v_{4 }

⇒ 0.1×2 + 0.2×1 = 0.1×1.67 + 0.2×v_{4}

⇒ 0.4 = 0.67 + 0.2×v_{4}

⇒ v4 = 1.165 m/s

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