I mean your average party balloon, when it’s completely deflated, it seems you have to put extra effort into getting it going. As soon as it starts inflating, you need less effort.
In: Physics
Think of the forces on a small piece of the balloon rubber. There is tension around the outside from the elasticity of the balloon material. Because of the curvature of the balloon, some of that elastic tension is pulling that piece of rubber inward. This force is countered by the pressure difference providing an outward force. If the balloon wall is in equilibrium, those forces should all cancel out. If you blow air into the balloon the pressure increases, and if the balloon expands the pressure decreases, so one way to think of it is that the balloon will change its size until the equilibrium state is reached.
Now, consider that the bigger a balloon is, the less curved any small segment of it will be. Even if the balloon material gets tighter as the balloon stretches, less of that tension is directed inward, meaning that less pressure is needed in the balloon to maintain equilibrium. When you blow up a balloon, your lungs are working against the pressure inside the balloon.
Overall, this means bigger balloon leads to less pressure needed to balance the tension of the balloon, which leads to less work your lungs have to do to blow it up.
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