Question

Why is it difficult to insert paper ball in bottle by blow of air?

Answer 1

Answer:

It is difficult because the pressure inside the bottle opposes our blow

Answer 2

It is not possible to insert a paper ball in to a bottle by air blow because air occupies the space around the paper ball leaving no space left for the ball to use or to fit in to the bottle.

Alternatively, if you pierce a small hole in the sides of paper ball using a sharp pin and then if you blow then you can pass the ball inside with the air blow.