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Question
It is easier to swim in sea water than in river water. Explain the reason.
Solution
The density of seawater is greater than the density of river water, [because of impurities]
- In each case, the weight of water displaced will be equal to the weight of the man.
∴ Ratio of weight of seawater and river water displaced by man is 1: 1. - With a smaller portion of man’s body submerged in seawater, the weight of seawater displaced is equal to the total weight of the body. While to displace the same weight of river water, a larger portion of the body will have to be submerged in water.
∴ It is easier for man to swim in seawater.
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