Advertisements
Advertisements
प्रश्न
Explain the following :
A balloon filled with hydrogen rises to a certain height and then stops rising further.
Advertisements
उत्तर १
The reason is that the density of air decreases with altitude. Therefore, as the balloon gradually goes up, the weight of the displaced air (i.e. uphrust) decreases. It keeps on rising as long as the upthrust exceeds its weight. When upthrust becomes equal to its weight, it stops rising.
उत्तर २
A balloon filled with hydrogen has low density than air so it rises over the air but as height increases density of air decreases and at a certain height the density of hydrogen in balloon and density of air become equal. And as there is no density difference there is no pressure difference also and hence balloon stops rising further.
संबंधित प्रश्न
A body of density ρ sinks in a liquid of density ρL. The densities ρ and ρL are related as :
A body of volume 100 cm3 weighs 5 kgf in air. It is completely immersed in a liquid of density 1.8 × 103 kg m-3. Find:
- The upthrust due to liquid and
- The weight of the body in liquid.
A piece of brass weighs 175 gf in air and 150 gf when fully submerged in water. The density of water is 1.0 g cm-3.
(i) What is the volume of the brass piece? (ii) Why does the brass piece weigh less in water?
Calculate the mass of air in a room of dimensions 4.5 m × 3.5 m × 2.5 m if the density of air at N.T.P. is 1.3 kgm-3 .
Explain the following :
An egg sinks in fresh water, but floats in a strong salt solution.
Explain the following :
Toy balloons filled with hydrogen rise to the ceiling, but if they are filled with carbon dioxide, then they sink to the floor.
A piece of wood of uniform cross section and height 15 cm floats vertically with its height 10 cm in water and 12 cm in spirit. Find the densities of wood and spirit.
A wooden block floats in water with two-third of its volume submerged.
(a) Calculate the density of wood.
(b) When the same block is placed in oil, three-quarters of its volume is immersed in oil. Calculate the density of oil.
The density of ice is 0.92 g cm-3 and that of sea water is 1.025 g cm-3. Find the total volume of an iceberg which floats with its volume 800 cm3 above water.
