Question

It is easier to swim in sea water than in river water. Explain the reason.

Answer 1

The density of seawater is greater than the density of river water, [because of impurities]

(i) In each case, the weight of water displaced will be equal to the weight of the man.
∴ The ratio of the weight of seawater and river water displaced by man is 1:1.

(ii) With a smaller portion of man’s body submerged in seawater, the wt. of sea water 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 ¡n water.
∴ It is easier for a man to swim in seawater.