Question

It is easier to swim in sea water as compared to fresh water because
A. Sea water exerts a greater force on the swimmer
B. Sea water exerts a lesser force on the swimmer
C. Sea water exerts an equal force on the swimmer
D. None of the above

Answer 1

Hint: Sea water is heavier and the swimmer displaces heavier things and hence receives higher reaction.

Complete step by step solution:
According to Archimedes Principle, the magnitude of buoyant force experienced is equal to the weight of liquid displaced by it by being placed in it.
Which means \[B = V{\text{ }}\rho {\text{ }}g\]
hence \[B \propto \rho \]
Since the density of seawater is greater due to presence of salts, than that of fresh water, the swimmer experiences higher buoyant force upwards and feels lesser weight and it is, thus, easier for him to swim.

So the correct option is (A), sea water exerts greater force on swimmers.

Additional information:
1. Archimedes' principle states that an object immersed in a fluid experiences a buoyant force that is equal in magnitude to the force of gravity on the displaced fluid. In other words it states that anybody completely or partially submerged in a fluid (gas or liquid) at rest is acted upon by an upward, or buoyant, force, the magnitude of which is equal to the weight of the fluid.
2. The Archimedes principle is also used in a large variety of scientific research subjects including engineering, medical and geology.

Note: (i) Archimedes' principle describes how ships float, submarines dive, hot air balloons fly,
(ii) Archimedes principle is useful in measuring the volume of irregular objects as well as in explaining the behaviors of any object placed in any fluid.