Why does a partially inflated weather balloon expand as it rises? the balloon itself stretches over time. air pressure inside the balloon decreases as the balloon rises. a change in temperature causes the balloon to expand. air pressure pushing in on the balloon decreases as the balloon rises.

So in an Inflated balloon, the pressure in the inside surface (the pressure by the gas inside the ballon) 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, this allows the surface of the balloon to grow, and the pressures can equilibrate.

Alson you can see it this way, as the outside pressure starts to decrease, there are less force holding the ballon size, then it can get a little bigger.

the design of a ski jumping suit involves a trade-off between giving the skiers lift to get higher jumps and ensuring the skier does not face a lot of drag before the jump itself. an expansive suit may to lift the skier higher, but at the same time, it will also increase the air resistance. higher air resistance as the skier goes down the slope limits the speed of the jump. a big suit also increases the risk of losing balance or control, especially if there's a strong gust of wind. while technologically enhanced suits a lot, clothing is not the only factor in a ski jumper’s success. gathering speed while skiing down the slope, ensuring good speed on the ramp, and maintaining good body posture and form in the air all contribute to a ski jumper's success.