Fluid Mechanics

Question 1

Science of fluid at rest is called

Answer 1

Fluid statics

Question 2

Fluid pressure

Answer 2

F/ change in area

Question 3

1 atm=

Answer 3

1.013 x 1^5 Pa

Question 4

1 Torricelli’s (torr) =

Answer 4

133 Pa

Question 5

Relative density

Answer 5

Is the ratio of density of a substance to the density of water at 4 C

Question 6

Pressure due to fluid column

Answer 6

h x density x g

Question 7

Gauge pressure =

Answer 7

Real pressure - atmospheric pressure

Question 8

Pascal’s Law

Answer 8

States that on changing the fluid pressure at any point the change is transmitted to the entire liquid without being diminished in magnitude

Question 9

Applications of pascals law

Answer 9

Hydraulic machines like hydraulic brakes,lift,etc.

Question 10

Archimede’s Principle

Answer 10

States that the loss in weight of a submerged body is equal to the weight of liquid displaced by it

Question 11

Mathematical form of Archimedes principle

Answer 11

V• =

V x [1 - (density of body /density of liquid)]

Question 12

Laws of floatation

Answer 12

States that if:
1] density of body > density of liquid –> it’ll sink

2]density of body = density of liquid–>
It’ll float fully submerged..I.e..just below the liquid surface

3]density of body
It’ll float partially submerged such that

V x density of body = Vim x density of liquid

Question 13

Continuity equation

Answer 13

Av = constant

Question 14

Pressure energy =

Answer 14

pAl

Question 15

Pressure energy per unit volume =

Answer 15

p

Question 16

Kinetic energy=

Answer 16

(1/2) x m x v^2

Question 17

Kinetic energy per unit volume =

Answer 17

(1/2) x density x v^2

Question 18

Potential energy=

Answer 18

mgh

Question 19

Potential energy per unit volume =

Answer 19

h x density x g

Question 20

Bernoulli’s Theorem

Answer 20

States that for a streamlined motion of an ideal fluid the total energy is always constant throughout

Question 21

Applications of Bernoulli’s Theorem

Answer 21

1] carburettor 
2] paint gun
3]scent sprayer and atomiser
4] Magnus effect
5] Aerofoil
6] Bunsen burner, gas burner, oil stove actions
7] Torricelli's Theorem
8] venturimeter 
9] pitot tube

Question 22

Limitations of Bernoulli’s Theorem

Answer 22

1] it’s applicable only to streamlined motion and not steady or turbulent flow since in these cases the velocity and pressure fluctuates with time

2] it’s applicable only to ideal fluids

3] at rest the Bernoulli’s Theorem changes to
(p-p’) = (h’-h) x density x g

Question 23

Torricelli’s law

Answer 23

States that efflux of water is same as that of a freely falling body under gravity

Question 24

Mathematical form of Torricelli’s Law

Answer 24

v = (2gh) ^1/2

Question 25

Volume of liquid coming out of an orfice

Answer 25

A x (2gh)^1/2

Question 26

Time period of liquid coming out of an orfice

Answer 26

T = (14||/15) x (R^5/2)/a(2g)^1/2

Question 27

Surface tension =

Answer 27

F/L

Question 28

Consequence of surface tension

Answer 28

Is that pressure inside a soap bubble is greater than the atmospheric pressure outside

Question 29

Excess pressure for a liquid/air drop

Answer 29

p = 2T/R

Question 30

Excess pressure for a soap bubble

Answer 30

p = 4T/R

Question 31

Increase in surface energy =

Answer 31

T x change in area

Question 32

Relation between angle of constant and temperature

Answer 32

Angle of contact increases with increase in temperature

Question 33

Relation between angle of contact and impurities

Answer 33

Angle of contact decrease with increase in impurities

Question 34

Rise in capillary tube =

Answer 34

h = 2T/ ( r x density x g)

Question 35

Rise in capillary if the tube is tilted by an angle @

Answer 35

l = h/cos@ where h is the rise in capillary when the tube is vertical

Question 36

For insufficient height of tube

Answer 36

hR = h'R'

Question 37

After connection of capillary tube

Answer 37

h = 2T /(r x density x g) - r/3

Question 38

While flowing in a tube the velocity of liquid is

Answer 38

Maximum along tube's axis 0 at tube's walls

Question 39

What kind of flow do liquids have and why?

Answer 39

Laminar flow due to viscosity

Question 40

Poiseuille's Formula

Answer 40

Vplume of liquid flowing per second = (|| x density x R^4) / 8 n L Where n-coefficient of viscosity

Question 41

Stokes Law

Answer 41

Force of viscosity = 6 || n r v Where n - coefficient of viscosity v - terminal velocity

Question 42

Terminal velocity=

Answer 42

v = (2/9) x [r^2 x (density of body - density of liquid) x g] / n Where n- coefficient of viscosity

Question 43

Reynolds Number(Re)

Answer 43

It tells us about the nature of flow of fluid

Question 44

Assumptions based on values of Reynolds number

Answer 44

Value. Flow Re3000. Turbulent 2000

Question 45

What will happen to pressure in the absence of intermolecular forces

Answer 45

Pressure will increase

Question 46

Work =

Answer 46

T x change in area