A ball having mass m and velocity u makes a head on collision with another ball. After collision velocity of the ball of mass m was found to be V in the direction of its original motion. The interaction force between the two balls during their collision has been shown in the graph. The area of the shaded part of the graph is same as the area of the not shaded part. Find the velocity of the balls at the instant they were having equal velocity.

Answer

`(u + V)/(2)`