Q. Six identical balls are linked in a straight groove made on a horizontal frictionless surface as shown. Two similar balls each moving with a velocity $v$ collide elastically with the row of 6 balls from left. What will happen
A) One ball from the right rolls out with a speed $2v$ and the remaining balls will remain at rest
B) Two balls from the right roll out with speed $v$ each and the remaining balls will remain stationary
C) All the six balls in the row will roll out with speed $v/6$ each and the two colliding balls will come to rest
D) The colliding balls will come to rest and no ball rolls out from right
Explanation
(b) Momentum and kinetic energy is conserved only in this case
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.