Question

Surface energy of water drop having radius r is directly proportional to _____? a)r3 b)r2 c)r d)1/r

Answer 1

(b) r^2

since we know that ---

surface energy = surface tension * Area

so,area= 4*pi*r^2

now,surface energy is proportional to 4 pi*r^2

hence r^2 is the answer.

Answer 2

The surface energy of water drop with a radius of drop being r is directly proportional to square of the radius $b) \ \ r^2$.

Explanation:

This is because of the fact that the energy is equal to the product of surface tension and area.

From there, the energy is directly proportional to the area.

The area of a drop is given below:

$Area =4 \pi(\text {radius})^{2}$

Thereby, from this proportionality equation, we can rule out the constant and derive the conclusion that the energy is proportional to square of radius.

$Surface \ Energy \propto (\text {Radius})^{2}$