Additional SEE Practice — Q1. Two identical balloons are released, one filled with air and the other with hydrogen. What difference do you expect and why?

Question

Accepted Answer

The hydrogen-filled balloon will rise into the air, while the air-filled balloon will simply fall or stay at the same level. This is because hydrogen is much less dense than the surrounding air, so the weight of air displaced by the hydrogen balloon (upthrust) is greater than the balloon's own weight, causing it to rise. The air-filled balloon has almost the same density as the surrounding air, so there is little or no net upward force.