WHY IS IT DIFFFICULT TO FORCE THE PAPER BALL INTO THE BOTTLE BY BLOWING INTO THE BOTTLE
This is because air occupies space.The ball will not go in by blowing because the remaining space in the bottle is already used up by the air, and there is no more space left for the ball to fit. But if we pierce a small hole in the side of the bottle and try to force the ball inside, then it will pass through as the air in the bottle goes out through the hole.