Thursday 26 October 2017
SSC JE : CIVIL ENGINEERING : 2016 : ALL SETS WITH ANSWER
Click on the link to download the pdf file :
Sunday 24 September 2017
Fluid Mechanics MCQ : Previous Year's Questions With Answer
Q1: Pitot tube is used to measure : (ISRO 2016)
A: Discharge
B: Pressure
C:Velocity
D:Static Pressure
Saturday 23 September 2017
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
BEST BOOK FOR FLUID MECHANICS BY R.K. Bansal : Basic and conceptual : https://amzn.to/2HXQj3O
Sunday 9 April 2017
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
