If you are student of the fsc part and studying the physics then you should be looking for the notes of fluid dynamics chapter of physics 11th class. Here we have published the 1st Year Physics Fluid Dynamics Notes pdf download or read online.
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Q. Discuss the terminal velocity of a paratrooper? Show its graph Answer
The terminal velocity of a falling body occurs during free fall when a falling body experiences zero acceleration This is because of the retarding force known as air resistance Air resistance exists because ai molecules collide into a falling body creating an upward force opposite gravity This upward force will eventually balance the falling body's weight It will continue to fall at constant velocity known as the terminal velocity The magnitude of terminal velocity depends on the weight of the falling body For a heavy object the terminal velocity is generally greater than a light object This is because air resistance is proportional to the falling body's velocity squared For an object to experience terminal velocity, air resistance must balance weight An example that shows this phenomenon was the classic illustration of a rock and a feather being dropped simultaneously In a vacuum with zero air resistance, these two objects will experience the same acceleration But on the earth this is not true Air resistance will equal weight more quickly for the feather than it would for the rock Thus the rock would accelerate longer and experience a terminal velocity greater than the feather Sky Driver
The graph shows how the vertical velocity of a parachutist changes from the moment the parachutist jumps from the aircraft until landing on the ground Using the idea of forces, explain why the parachutist reaches a terminal velocity and why opening the parachute reduce the terminal velocity
Another factor that affects terminal velocity is the onentation at which a body falls If an object falls with a larger surface area perpendicular to the direction of motion it will experience a greater force and a smaller terminal velocity On the other hand if the object fell with a smaller surface area perpendicular to the direction of motion, it will experience a smaller force and a greater terminal velocity
Q. What is the difference between steady and turbulent flow? What is an ideal fluid?
Answer
Fluid Flow
Let us consider the flow of the fluid through the pipes It may be either streamline or turbulent
Laminar Flow.
The flow of a fluid in which every particle of the fluid moves along a smooth path is called laminar flow.
Turbulent Flow
When the speed of flowing fluid exceeds a certain critical value. the flow becomes extremely irregular and complex and it changes continuously with time Thus, The irregular or unsteady flow of the fluid is called turbulent flow Difference between Laminar Flow and Turbulent Flow
In laminar flow, each particle of fluid moves along a smooth path which does not change with time
In turbulent flow the flow pattern is not smooth but continuously changes with time In laminar flow stream lines do not cross each other while in turbulent flow it does not happen In turbulent flow the velocity of fluid changes abruptly Not (Steady flow condition)
For study flow, different streamlines can never intersect each other This conditions called steady flow condition
Ideal Fluid
A fluid which satisfies the following condition is called an ideal fluid
1) The fluid is non-viscous there is no internal frictional force between adjacent layers of fluid
2) The fluid is incomprehensible i.e its density is constant
3) The fluid motion is steady
4) Irrational flow
Q. State and explain equation of continuity.
Answer
Equation of Continuity
For an ideal fluid the product of cross sectional area of the pipe and the fluid speed at any point along the pipe is a constant OR
For an ideal fluid, the volume flow per second of the fluid (or simply flow rate) always remains constant
Q. How swing produced in a tennis ball?
Answer
Swinging of ball
Consider a tennis ball moving through air from left to right (shown in figure) in such a way that it spins as as move forward The steam lines of air appear to move from right to left The layers of air near the surface of ball are pulled around in the direction of spin due to friction between the ball and the air
The speed of air at top of the ball increases than at bottom In this case the average pressure at the top of ball becomes smaller than that at the bottom This gives an extra curvature to the ball known as swing, which deceives an opponent player
Q. What do you know about blood pressure? How it can be measured dynamically?
Answer
Blood is an incompressible fluid Density of blood is nearly equal to that of water
Viscosity of blood increased three to five times that of water due to high concentration of red blood cells (-50%)
Blood Pressure (BP)
The pressure exerted by the circulating blood on the walls of the blood vessels is called blood pressure
Blood vessels are not rigid Under normal conditions, the volume of the blood is sufficient to keep the vessels inflated at all times So the pressure of the blood inside the vessels is greater than atmospheric pressure During each heart beat BP vanes between a maximum (systolic) and a minimum (diastolic) pressure
A person's BP is usually expressed in terms of the systolic pressure over diastolic pressure (mmHg), for example 120/80Systolic Pressure. It represents the maximum pressure exerted when the heart contracts . The value of high blood pressure (systolic pressure) is 120 torr Diastolic Pressure
It represents the minimum pressure in the arteries when the heart is at rest The value of low blood pressure (diastolic pressure) is about 75-80 torr
Note The value of blood pressure increased with age due to decrease in the flexibility of vessels Unit of blood pressure
The blood pressure is measured in torr or mm of Hg
Measurement of Blood Pressure
Sphygmomanometer is used to measure the pressure of blood dynamically in the vessels
Steps to measure blood pressure
- An inflatable bag is wound around the arm
- The bag is inflated to increase the external pressure on the arm to compress the blood vessels inside
- When the external pressure becomes larger than systolic pressure, the vessels fall down The flow of blood is cut off.
- Head of a stethoscope is placed over the artery
Systolic Pressure
- Open the release valve to decrease the external pressure gradually
- When external pressure becomes equal to systolic pressure, the vessel opens a little bit
- A first surge of blood flows out of the narrow opening of vessel with high speed
- As the flow speed is high so the flow is turbulent
- At this instant, we hear a gurgle in the stethoscope
- This is signal to record systolic pressure
Diastolic Pressure
- Now decrease the external pressure further till it becomes equal to diastolic pressure
- The vessel gets normal
- The blood flow changes from turbulent to laminar
- The gurgle in the stethoscope disappear
- This is time to record diastolic pressure
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