Advertisements
Advertisements
Question
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?
Advertisements
Solution 1
(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.
Solution 2
(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.
RELATED QUESTIONS
Define the term density.
Explain why an iron nail floats on mercury, but it sinks in water.
Hint : Density of iron is less than that of mercury, but more than that of water.
What can you say about the average density of a ship floating on water in relation to the density of water?
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?
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.
A trawler is fully loaded in sea water to maximum capacity. What will happen to this trawler, if moved to river water? Explain your answer.
Select the correct option:
The ratio between the mass of a substance and the mass of an equal volume of water at 4°C is called:
Write the SI units of Weight of a body
A wooden cube of side 10 cm has a mass of 700 g. It will float in the water with:
(a) Half of its volume inside the water
(b) 3 cm height above the water surface
(c) 7 cm height above the water surface
(d) Just inside the water surface.
