Physics
A balloon does not rise indefinitely because :
- the density of air increases with altitude
- the density of air decreases with altitude
- the weight of the displaced air increases.
- None of the above
Answer
the density of air decreases with altitude
Reason — A balloon does not rise indefinitely because the density of air decreases with altitude. Therefore, as the balloon gradually goes up, the weight of the displaced air decreases. It keeps on rising as long as the upthrust on it exceeds its weight. When upthrust becomes equal to its weight, it stops rising further.
Related Questions
If a submarine is to dive, its ballast tanks are ……………, so that the average density of the submarine becomes …………… than the density of sea water.
- filled with water, greater
- filled with water, lower
- emptied, greater
- emptied, lower
Ice bergs float on the surface of water with their …………… portion inside the water surface and …………… portion above the water surface.
- smaller, larger
- larger, equal
- smaller, smaller
- larger, smaller
When a fish has to rise up in water, it diffuses oxygen gas from its blood into the bladder, so its volume …………… and its average density …………… .
- decreases, decreases
- increases, decreases
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- increases, increases
State the principle of floatation.