Question

Two air bubbles in the water
A. Attract each other
B. Repel each other
C. Neither attracts nor repel
D. None of these

Answer 1

Here, we use the concept of gravitational force, which says that the force of attraction between two bodies is directly proportional to the product of their masses and inversely proportional to the square of the distance between them.

Complete step by step answer:
Consider two air bubbles A and B in water. Where water acts as a denser medium in which a lighter body behaves like a negative mass as far as gravitational attraction is concerned. So by Newton’s law of gravitation
${\rm{F = G}}\dfrac{{{{\rm{m}}_1}{{\rm{m}}_2}}}{{{{\rm{r}}^2}}}$
Here F is the force of gravitation, $G$ is the gravitational constant, and ${{\rm{m}}_1}{\rm{,}}{{\rm{m}}_2}$ are the masses of two bodies and r is the separation between two masses.
But in water, both the bubbles have negative masses
$\Rightarrow {\rm{F = G}}\dfrac{{{\rm{( - }}{{\rm{m}}_1}{\rm{)( - }}{{\rm{m}}_2})}}{{{{\rm{r}}^2}}}$
$\therefore {\rm{F = G}}\dfrac{{{{\rm{m}}_1}{{\rm{m}}_2}}}{{{{\rm{r}}^2}}}$

This shows that force has attractive nature between two air bubbles in the water. Therefore, the correct option is (A).

Additional information:
The formation of the air bubble takes place when water is boiled; the heat energy is transferred to the molecules of water, which begin to move more quickly. Eventually, the molecules have too much energy to stay connected as a liquid. When this occurs, they form gaseous molecules of water vapor, which float to the surface as bubbles and travel into the air.

Note:
Gravitational force is always attractive and they can operate for very long distances. It obeys the inverse square law and is also called a conservative force. In gravitation law, $G$ is the universal gravitational constant whose value remains constant throughout the universe.