Question

In which of the following situations fluid friction is not acting?​
1) Between layers of same liquid​
2) A box placed on a floor in a vacuum chamber​
3) Airplane flying in atmosphere​
4) Satellite revolving around the earth​
5) Between layers of same gases

Answer 1

Fluid friction acts between the surfaces when any one or both the surfaces are liquid.
1. Fluid friction will act between the layers of the same liquid.
2. When vacuum is created, that means there is no air means no fluid is present. So, no fluid friction will act on the box placed on ground in vacuum.
3. Airplanes while flying in the atmosphere have to experience drag due to air which is again a fluid.
4. Satellite is revolving around the earth in space and we know that there is no atmosphere in space. Hence, staellite will not experience any fluid friction.
5. Gases are fluids. Hence, fluid friction will be acting between the layers of the gases as well.

We can conclude that fluid friction is not acting in case 2 and 4.