A hydrogen balloon floats up because of (a)air pressure decreases with decrease in height (b)air pressure decreases with decrease in weight (c)weight of the balloon is less than the weight of air displaced by it. (d)the pressure inside the balloon is more than the pressure outside it
option c. The balloon has to displace a few air, so in response, the air pushes up on it. But hydrogen is much less dense than air, so the air pushes up at the balloon more difficult than gravity is pulling it down, and the balloon attempts to transport up. So similar to timber drift on water, hydrogen balloons glide on air.
