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प्रश्न
A man first swims in sea water and then in river water. (i) Compare the weights of sea water and river water displaced by him.
(ii) Where does he find it easier to swim and why?
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उत्तर १
(i) 1:1; The weight of the water displaced by the man in sea and river will be same and will be equal to his own weight.
(ii) He finds it easier to swim in the sea because the density of sea water is more than the density of river water. So his weight is balanced in sea water with a part of his body submerged in the water.
उत्तर २
(i) When a body is completely immersed in water then it displaces an equal volume of water to its own weight. The volume of the body of man is the same in both river and sea so the weight of the water of the sea displaced by him is equal to the weight of the water of the river displaced by him. And the ratio of weights would be 1:1.
(ii) Sea water contains mineral salts and the density of sea water increases due to the presence of these. As the density of sea water is more than the normal water so it applies more buoyant force than the usual one and a person finds it easy to swim in sea water.
संबंधित प्रश्न
Assuming the density of air to be 1.295 kg m-3, find the fall in barometric height in mm of Hg at a height of 107 m above the sea level. Take density of mercury = 13.6 × 103 kg m-3.
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?
What are the units density in (i) C.G.S. and (ii) S.I. system .
'The density of iron is 7800 kg m-3'. What do you understand by this statement?
A jeweller claims that he makes ornaments of pure gold that has a relative density of 19.3. He sells a bangle weighing 25.25 gf to a person. The clever customer weighs the bangle when immersed in water and finds that it weighs 23.075 gf in water. With the help of suitable calculations, find out whether the ornament is made of pure gold or not.
[Hint : calculate R.D. of material of bangle which comes out to be 11.6].
Explain the following :
As a ship in harbour is being unloaded, it slowly rises higher in water.
A rubber ball floats on water with its 1/3rd volume outside water. What is the density of rubber?
A piece of wax floats on brine. What fraction of its volume is immersed?
Density of wax = 0.95 g cm-3, Density of brine = 1.1 g cm-3.
Complete the following result:
Density in kg m-3 = ______ x density in g cm-3
