# Collision of billiard balls

The masses of the blue ball (#$$10$$) and the purple ball (#$$12$$) are $$2$$ kg and $$1$$ kg, respectively. Now, the blue ball with a velocity of $$4$$ m/s collides with the purple ball which was standing still. After the collision, the blue ball keeps moving in the same direction with a reduced velocity of $$2$$ m/s. What is the velocity of the purple ball after the collision?

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