Viscosity With Exams Based MCQ IMP for GATE , SSC JE , PSU

Viscosity : It is the property of the fluid  which opposes the relative motion between the two surfaces of the fluid in a fluid that are moving a different velocity.

Viscosity can be two types:

1: Dynamic Viscosity Or Absolute Viscosity Or Coefficient of Viscosity or Viscosity

2: Kinematic Viscosity ( This is imaginary not really present in real life)

The main difference between Dynamic viscosity and Kinematic Viscosity is:

Dynamic Viscosity: One way is to measure a fluid's resistance to flow when an external force is applied , This is Dynamic viscosity , always it is used for practical purpose.


Units: SI : N.S/ m2

C.G.S Unit: Dyne-Sec/ Cm2 ( It is also called Poise)

M.K.S. Unit: Kgf-Sec/ m2


Kinematic Viscosity: The other way is to measure the resistive flow of a fluid under the weight of gravity , the result is kinematic vicosity . Do not use it by your own, until  there is no mention of particulate word (Kinematic Viscosity) in numerical .

Units:  SI : m2/s

CGS unit: cm2/sec ( It is called stoke )

M.K.S =m2/Sec

IMP Point:-

Two fluid that have the same Dynamic viscosity can have different kinematic viscosity  This is due to kinematic viscosity dependent on the density of the fluid , density is not a factor with Dynamic viscosity .

Some Other Key Points regarding Viscosity:


1: The dynamic viscosity of pure water at 20 degree Celsius is 0.01 poise or 1 centi poise

2: The viscosity of fluid decreases with increasing the temperature ( Because fluid has a tendency to flow in stream line in most of the cases , when velocity of flow is low)

3: The viscosity of gases increases with increasing the temperature ( REASON:  when we heat the gases then gas molecules travel in zig zag motion, so the momentum of gases particles increases and they generate high shear stress due to high momentum)

4: Water has higher viscosity than Mercury.

 Now test youself  : MCQ :  based on Viscosity:

Q1: Poise is the C.G.S unit of:
A: Viscosity
B: Kinematic Viscosity
C: Surface Tension
D: Capillary


 Q2: C.G.S unit of Kinematic Viscosity is:
A: Newton-Sec
B: Stoke 
C: Dyne
D: Poise

Q3: The increase of the temperature :
A: Increase the viscosity of liquid
B Increase the viscosity of gases 
C: Decrease the viscosity of gases
D: No effect


 Q4: Newton law of viscosity states that :

A: shear stress is directly proportional to the velocity
B: Shear stress is directly proportional to velocity
C: shear stress is directly proportional to rate of shear strain
D: Shear stress is directly proportional to the viscosity

Q5: Which has higher viscosity : A : Mercury, B: Water  

Q6:  What measures a material's resistance to flow?
  


A: Matter , B: Volume C: Viscosity, D: Surface Tension
Q7: When friction increases what else increases?                                                                                        A: Elasticity , B: Density , C: Viscosity, D: Matter


 







                                                                                

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Interviews and Exams questions : ALL About Cement

1: Name the component that responsible for early strength of concrete:

Ans: C3S ( Tri Calcium silicate ) , that react with water and produces more heat of hydration is responsible for early strength of concrete.

2: Which compound contribute to the later strength of concrete ?

Ans: C2S ( Di Calcium silicate ) that hydrates slowly , contribute to the later strength of concrete .

3: After how many days , the compressive strength developed by C3S and C2S are equal .

Ans: ONE year  

4:For road rapid work which type of cement is recommended :

Ans: Rapid hardening cement

5: In how many  days , about 50% of the total heat evolution occurs.

Ans: During the first 3 days of hydration 

6:Which oxides are responsible for high early strength of cement ?

Ans: High total alumina and high ferric oxide content favour the production of high early strength in cement

Compounds : When components of cements added up with water than they called compound in simple language ..

Tricalcium Silicate (C3S) hardens rapidly and is largely responsible for initial set and early strength.

In general, the early strength of portland cement concrete is higher with increased percentages of C3S.

Dicalcium Silicate (C2S) hardens slowly and contributes largely to strength increases at ages beyond 7 days.

Tricalcium Aluminate (C3A) liberates a large amount of heat during the first few days of hardening and, together with C3S and C2S may somewhat increase the early strength of the hardening cement (this effect being due to the considerable heat of hydration that this compound evolves). It does affect set times.

Tetracalcium Aluminoferrite (C4AF) contributes very slightly to strength gain. However, acts as a flux during manufacturing. Contributes to the color effects that makes cement gray.aakes cement gray.

Compounds by percentage :

Role of compounds on properties of cement : MOST IMP

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1: http://amzn.to/2iMfgUj (Reinforced Concrete Design - Third Edition ) by Devdas Menon (Author), S. Pillai (Author)

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TOP 7 : STEEL STRUCTURE

1: With percentage increase of carbon in steel , decreases its
A: Strength
B: Hardness
C: Brittleness
D: Ductility  

2:Poisson's ratio for steel within elastic limit , ranges from
A: 0.15 TO 0.20
B: 0.25 TO 0.24
C: 0.25 TO 0.33
D: 0.33 TO 0.35

3: The slenderness ratio of a column is zero when its length 
A: IS ZERO
B: IS EQUAL TO ITS RADIUS OF GYRATION
C: IS SUPPORTED ON ALL SIDES THROUGHOUT ITS LENGTH
D: IS BETWEEN THE POINTS OF ZERO MOMENTS

4:Maximum permissible slenderness ratio of compression members which carry dead and superimposed load, is
A:350
B:250
C:180
D:80

5:The effective length of a weld, is taken as the actual length
A: Minus the size of weld
B: Minus twice the size of weld
C: Plus the size of weld
D: Plus twice the size of weld

6:A beam is defined as a structural member subjected to
A: Axial loading
B:Transverse loading
C: Axial and transverse loading

7:The best compression member section for column is:
A: Single angle section
B: Double angle section
C: Channel section
D: I-section

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Los Angeles Abrasion Test , Why and How To Perform

LOS ANGELES ABRASION TEST:

This is hardness test for aggregates, used in Laboratory  to determine the hardness value or abrasion value 

APPARATUS :

 Los Angeles Abrasion Testing Machine ,

Abrasive Charge – Cast iron or steel balls ,
Test sieve – 1.70 mm IS sieve ,

 Balance of capacity 10 kg , Oven , Tray

The aggregate used in surface course of the highway pavements are subjected to wearing due to movement of traffic. 

When vehicles move on the road, the soil particles present between the pneumatic tyres and road surface cause abrasion of road aggregates. 

The steel reamed wheels of animal driven vehicles also cause considerable abrasion of the road surface. 

Therefore, the road aggregates should be hard enough to resist abrasion. 

The principle of Los Angeles abrasion test is to produce abrasive action by use of standard steel balls which when mixed with aggregates and rotated in a drum for specific number of revolutions also causes impact on aggregates. 

The percentage wear of the aggregates due to rubbing with steel balls is determined and is known as Los Angeles Abrasion Value.

Key point of los angles test:

Rotate the machine at a speed of 30 – 33 revolutions per minute. The number of revolutions is 500 for grading A, B, C & D and 1000 for grading E, F & G. The machine should be

5 kg of sample for grading A, B, C & D and 10 kg for grading E, F & G

THE CALCULATION PART:

Original weight of aggregate sample = W1 g

Weight of aggregate sample retained = W2 g

Weight passing 1.7mm IS sieve = W1 - W2 g

Los Angeles Abrasion Value = (W1 - W2) / W1 X 100

Los angeles abrasion value should lies in below given range for different types of roads

Types of pavement layers                                         Max. Permissible Abrasion Value in %

1:WBM , SUB BASE COURSE                                                      60%

2:WBM BASE COURSE WITH BITUMEN SURFACE               50%

3: BITUMEN BOUND MACADAM                                             50%

4:WBM SURFACING COURSE                                                    40%

5: BITUMINOUS PENETRATION MACADAM                              40%

6:BITUMINOUS SURFACING DRESSING CEMENT
 CONCRETE SURFACING COURSE                                              35%

7:BITUMINOUS CONCRETE SURFACING COURSE                   30%

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TOP RCC QUESTIONS PART 2

12: The percentage of minimum reinforcement of the gross sectional area in slabs is:
A: 0.10%
B:0.12%
C:0.15%
D:0.18%

13: The amount of reinforcement for main bars in a slab is based upon:
A: Minimum bending moment
B: Maximum bending moment
C:Maximum shear force
D: Minimum shear force

14: In under reinforced singly reinforced beam , concrete crushes at its maximum strain
A: 0.35 %
B: 0.24%
C: 0.30%
D:0.20%

15: The maximum area of tension reinforcement in beams shall not exceed
A:0.15%
B:1.5%
C:4%
D:1%

16: A raft foundation is provided if its area exceeds the plan area of the building by: 50%

17: For a number of columns constructed in a row , the type of foundation provided is: Strip 

18 : As per IS :456, the reinforcement in a column should not be less than : 0.7 % and more than 7% of cross sectional area

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