Two identical ball bearings in contact with each other and resting on a frictionless table are hit head - on by another ball bearing of the same mass moving initially with a speed V. If the collision is elastic , which of the following fgures is a possible result after collision ?

Explanation

Suppose , the mass of every ball of ball bearing is m ,
The total kintic velocity of a system before collision ,
`=1/2 mv^(2)+0 " " [ :. "Velocity of ball 1 = v and velocity of ball 2=0 "]`
After collision , kinetic energy of the system in various cases ,
Case 1 : `E_(1) =1/2 (2m)(v/2)^(2) =1/4 mv^(2)`
Case 2 : `E_(2) =1/2 mv^(2)`
Case 3: `E_(3) =1/2 (3m) (v/3)^(2)`
` =1/6 mv^(2)`
Hence , Case 2 is the only possibility . Since , kinetic energy is conserved i this case .