Question

When we prick a balloon it bursts ?

Answer 1

When you inflate a balloon, the air pressure inside it is much more than the atmospheric pressure outside of it. If the balloon is pricked, all the air comes tries to come out with great force. This small hole cannot allow so much of air to go out at once. Also, now that there is weak spot in the membrane, the pressure due to the air tears apart the rubber in an instant.

So, this is the reason why a balloon bursts when pricked.