Question

why does the stack of carrom coins fall down vertically?

Answer 1

this is because of newtons first law of motion which tells about this reason that when the lower coin is hit by the striker it moves and comes in motion while other remain due to inertia of rest hence they fall down

Answer 2

this is due to Newton's first law of motion
the reason is that as the striker hits the lowest coin it more changes its state or rest while the remaining file due to inertia of rest remain where it is and ultimately take the place of original file due to force of gravity..