Question

A large ship can float but a steel needle sinks because of
A) viscosity
B) surface tension
C) density
D) none

Answer 1

For a body to float on water, the weight of the body must be equal to the upthrust or the buoyancy force. On comparing these two formulas, we will get to know the reason why ship floats and needle sinks. The upthrust force depends on the density of liquid whereas the weight of the body is related to the density of the body.

Complete answer:
Water is impossible to compress. Its high density means it can exert a lot of pressure on the bodies floating. It exerts force in every direction. When a ship is placed on water, we can observe the ship occupy a huge volume of space so that all its weight is spread across the water. For the boat, the net force acting on the boat will be upwards because water pressure is balanced in every direction except upwards. This upward force on the boat or ship is called an upthrust force. Also, the more the ship weighs, the lower the ship sinks.

Therefore, the ship floats but the needle sinks are all because of the surface area of the body.

So, the correct answer is “Option D”.

Additional Information:
The Archimedes principle stated that when a body is fully or partially submerged in a fluid, a buoyancy force from the surroundings acts on the body, this force is in the upward direction and has a magnitude equal to the weight of the fluid that has been displaced by the body.

Note:
In the buoyancy force formula, the density depends on the density of the liquid on which the object is floating. Whereas, in case of the weight, the density is the density of the body floating in the liquid. Also, the more the surface area, the lesser the body sinks in the liquid due to the more upward force acting on the body.