CHAPTER 6 FLUID DYNAMICS

 

6.1      Multiple choice questions.

1.      Viscosity of a fluid depends upon
(a) Mass	(b) Density
(c) Volume	(d) Temperature
2.      Drag force exerted by the fluid on a body does not depend upon
(a) Viscosity of fluid	(b) Terminal velocity
(c) Shape of a body	(d) Volume of fluid
3.      A steel ball of radius ‘r’ is moving with uniform velocity ‘v’ in the mustard oil, the drag force acting on the ball is ‘F’. What would be the drag force on the steel ball of radius 2r moving with uniform velocity 2v in the mustard oil is
(a) F	(b) 2F
(c) 4F	(d) 8F
4.      When two spheres of same volume but different masses fall through a fluid then
(a) Both gain their terminal velocity simultaneously	(b) Neither lighter nor heavier body gains its terminal velocity
(c) Lighter body gains its terminal velocity earlier	(d) Heavier body gains its terminal velocity earlier
5.      Laminar flow usually occurs at speeds
(a) Low	(b) High
(c) Very High	(d) Some time high & some time low
6.      In incompressible fluid, which parameter remains constant?
(a) Pressure	(b) Volume
(c) Temperature	(d) Density
7.      Equation of continuity has been derived on the bases of law of conservation of
(a) Energy	(b) Energy
(c) Mass	(d) Force
8.      According to equation of continuity A1v1= A2v2 = constant. The constant is Equal to
(a) Flow rate	(b) Volume of fluid
(c) Mass of fluid	(d) Density of fluid
9.      When cross-sectional area of a tube is decreased then the speed of fluid through it is;
(a) Increased	(b) Decreased
(c) Same	(d) Zero
10.  As the water falls its speed increases, so its cross-sectional area
(a) Increases	(b) Decreases
(c) Remains constant	(d) Zero
11.  Bernoulli’s equation has been derived on the bases of conservation of;
(a) Mass	(b) Energy
(c) Momentum	(d) Force
12.  What is the speed of water flow through a tap which is connected with tank contains water at height of 2.5 m .
(a) 5 ms-1	(b) 6 ms-1
(c) 7 ms-1	(d) 8 ms-1
13.  A two-meter high tank is full of water. If a hole appears at its middle, then the speed of efflux is
(a) 4.42 ms -1	(b) 5.42 ms -1
(c) 6.42 ms -1	(d) 7.42 ms -1
14.  Venturi-meter is an instrument which is being used for the measurement of
(a) Density of fluid	(b) Velocity of fluid
(c) Pressure of fluid	(d) Viscosity of fluid
15.  When velocity of fluid is increased then its pressure is;
(a) Increased	(b) Decreased
(c) Same	(d) Not velocity dependent
16.  Systolic pressure is called;
(a) Low blood pressure	(b) High blood pressure
(c) Normal pressure	(d) irregular blood pressure

 

Answers

1. (d) Temperature
2. (d) Volume of fluid
3. (c) 4F
4. (d) Heavier body gains its terminal velocity earlier
5. (a) Low
6. (d) Density
7. (c) Mass
8. (c) Mass of fluid
9. (a) Increased
10. (b) Decreases
11. (b) Energy
12. (c) 7 ms-1
13. (a) 4.42 ms -1
14. (b) Velocity of fluid
15. (b) Decreased
16. (b) High blood pressure 

6.2      Short question

7. How can transfer the laminar flow into the turbulent flow?

ans.    Laminar flow can be changed into turbulent flow by introducing disturbances into the flow or increase the velocity of the fluid.

9. What are the three factors associated with an ideal flow?

ans.         Characteristic of ideal flow

• The fluid is non-viscous.
• The flow is steady.
• The fluid is incompressible. 

14. What is the difference between systolic and diastolic reading of blood Pressure?

ans.    The systolic pressure is the maximum pressure your heart exerts while diastolic pressure is the amount of pressure in your arteries between the beats.

6.3      Numerical problems

1.  A metal sheet of area 0.4 m² is attracted by a force of 0.98 N over a liquid thin Film lies between sheet and surface of table of thickness 0.2 mm. If the sheet starts its motion with uniform velocity    0.2 ms^‑1. Calculate the co-efficient of viscosity of the liquid.

5. Water flows through a horizontal pipe of non-uniform cross-sectional area. The pressure is 130k pa where the velocity is 0.4 ms^-1. Calculate the pressure at the point where the velocity is 4 ms^-1.

7. what is the height of water containing in tank? When the velocity of efflux of a water through 

orifice from the tank 9.9 ms^-1.

8. A liquid of density 8x10³ kgm^-3 is flowing through a horizontal pipe of Different cross section. If the pressure difference between two points is 4 x 10⁴ Nm^-2 then what is the speed of liquid in the tube.