Students can go through AP Inter 1st Year Physics Notes 11th Lesson Mechanical Properties of Fluids will help students in revising the entire concepts quickly.
AP Inter 1st Year Physics Notes 11th Lesson Mechanical Properties of Fluids
→ The property by virtue of which a liquid opposes the relative motion between its layers is called viscosity.
→ If the velocity of any point in the flow is independent of time is called streamline flow.
→ The velocity during the streamline flow is less than a particular velocity called critical velocity.
→ If the streamlines are parallel, the flow is called laminar flow.
→ Pressure difference at different depths in a fluid cause an upward thrust on an object immersed in the fluid. This upward thrust is called buoyant force. Buoyant force is equal to the weight of the fluid displaced by the immersed body.
An object floats on a fluid if its density is less than that of the fluid.
Fraction of the volume of the object submerged in a fluid is equal to the ratio of density of the object to density of the fluid.
→ Study of moving fluids is called fluid dynamics. Flow of fluids is of two types
- Streamline flow
- turbulent flow.
→ Fluid flow may be
- steady or non-steady,
- rotational or irrotational,
- compressible or incompressible and iv. viscous or non-viscous.
→ A line in a fluid on which, a tangent drawn at every point represents the direction of velocity of the fluid is called a streamline.
The density of streamlines at a point is proportional to the magnitude of the fluid at that point. If streamlines coincide with the trajectories of the flowing fluid particles, the flow is called a steady flow.
Bundle of streamlines is known as a tube of flow.
→ If the velocity of the fluid at a point varies with time the flow is called turbulent flow.
→ The minimum velocity of the fluid at which the flow changes from streamline to turbulent flow is called critical velocity.
→ For a steady flowing fluid in a pipe the product of cross sectional area A and velocity of the fluid v at a point is constant.
AV = constant.
This is known as equation of continuity.
→ The motion of objects in flowing fluid can be understood by Bernoulli theorem. It is stated like this:
For a steady flow of a non-viscous, incompressible fluid sum of the pressure energys kinetic energy and the potential energy per unit volume remains constant at all points. The equation is given by
P + ρgh + \(\frac{1}{2}\) ρ v2 = constant.
→ The frictional force between the successive layers of a flowing fluid is called viscous force. This frictional force hampers the flow of the fluid.
The property of a fluid which opposes the relative motion between, different layers is called viscosity.
→ Viscous force F = –\(\eta \mathrm{A}\left(\frac{\Delta \mathrm{v}}{\Delta \mathrm{x}}\right)\)
→ Stokes law: The viscous force F acting on a smooth spherical body .which is moving in a fluid is given by
F = 6 πη r v
h coefficient of viscosity of the fluid r is the radius of the spherical body, v the velocity of the body in the fluid.