Question

In terms of physics, which of the following are considered fluids?
A) Solids and gases
B) Gases and liquids
C) Only liquids
D) Liquids and solids

Answer 1

Hint: Fluids are the substances that cannot resist any external forces applied to it. The fluids continuously change their shape and get deformed on applying shear stresses. The fluid has the ability to flow and it takes the shape of the container in which it is. It has many properties like compressibility, viscosity, surface tension. But the value for each fluid is specific for it.

Complete step by step answer:
Fluids have very low resistive force applied to it. And it attains deformation when the force is applied. In physics, the term ‘fluids’ represents liquids and gases.

Hence the correct option is B.

Additional information:
(i) Fluids have many properties. The extensive properties are mass and volume. And the intensive properties are density, temperature, and pressure. All fluids have these properties. But the value of each property is specific to every fluid.
(ii) The three physical properties which are specific to fluids are viscosity, surface tension, and density.
(iii) Viscosity is the measure of resistive force against the deformation due to the shear force. In SI units, viscosity is measured in Pascal second. And the viscosity of the fluid increases with an increase in temperature.
(iv) Surface tension is the tendency of the liquid to shrink into the surface. It is also an attractive force between the surface molecules in the liquid and the molecules beneath the surface.

Note:
Fluids are substances that have very low resistive force. So, it will be deformed on the application of external force on it. It has its own property like viscosity and surface tension. It has the ability to flow and acquire the shape of the container. And the molecules inside the fluids are comparatively arranged freely to solids.