Four smooth steel balls of equal mass at rest are free to move along a straight line without friction. The first ball is given a velocity of 0.4 𝑚/𝑠. It collides head on with the second elastically, the second one similarly with the third and so on. The velocity of the last ball is

Four smooth steel balls of equal mass at rest are free to move along a straight line without friction. The first ball is given a velocity of 0.4 𝑚/𝑠. It collides head on with the second elastically, the second one similarly with the third and so on. The velocity of the last ball is

Question: Four smooth steel balls of equal mass at rest are free to move along a straight line without friction. The first ball is given a velocity of 0.4 𝑚/𝑠. It collides head on with the second elastically, the second one similarly with the third and so on. The velocity of the last ball is