What makes a balloon inflate?
An inflated balloon is a physics system in equilibrium. Adding more air to the balloon creates an imbalance to the system, causing the balloon to fill with air and inflate.Air Pressure vs. Air PressureTo inflate a balloon, the air pressure being blown into the balloon must overcome or be greater than the static air pressure of the environment outside the balloon.Air Pressure vs. Surface TensionTo inflate a balloon, the air pressure being blown into the balloon must overcome or be greater than the balloon’s surface tension, or stretchiness.Cumulative PressureA balloon inflates whenever the sum of all pressures inside the balloon exceeds the sum of all pressures outside the balloon. Therefore, to inflate the balloon, the pressure inside from adding air must overcome both the outside air pressure and the balloon’s surface tension at the same time.Inflation by Withdrawing AirA reduction in outside air pressure can inflate a balloon if the inside air pressure remains unchanged. For example,
