Why does a partially inflated weather balloon expand as it rises?

What are the reasons for a partially inflated weather balloon expanding as it rises?

Choose the correct answer:

A. The balloon itself stretches over time.

B. Air pressure inside the balloon decreases as the balloon rises.

C. A change in temperature causes the balloon to expand.

D. Air pressure pushing in on the balloon decreases as the balloon rises.

Answer:

So in an Inflated balloon, the pressure in the inside surface (the pressure by the gas inside the balloon) must be equal to the pressure applied on the outside surface. As the balloon rises, the outside pressure starts to decrease, so the pressure inside must decrease, allowing the surface of the balloon to grow and the pressures can equilibrate.

When a partially inflated weather balloon rises, it expands due to the change in air pressure. As the balloon ascends, the air pressure in the atmosphere decreases. This decrease in pressure causes the pressure inside the balloon to also decrease. The pressure inside the balloon needs to be in equilibrium with the external pressure to maintain its shape and size.

Think of it this way: initially, when the balloon is at a lower altitude, the pressure inside the balloon is higher than the surrounding air pressure, keeping the balloon inflated. However, as the balloon rises and the external pressure decreases, the pressure inside the balloon also decreases. This decrease in pressure allows the balloon's surface to expand, making it appear inflated.

This phenomenon can also be explained by the fact that the air pressure pushing in on the balloon decreases as the balloon rises. With less force holding the balloon's shape, it is able to slightly expand, giving the impression of expansion as it ascends.