BUOYANCY LAW

 A  fundamental idea in physics, the buoyant force experienced by an object submerged in a fluid BUOYANCY LAW (liquid or gas) is explained by the buoyancy law, sometimes referred to as Archimedes' Principle. The Greek mathematician and scientist Archimedes is honoured by the name of this concept.

The Buoyancy Law is broken down as follows:

1. Buoyant Force:

The upward force that an object receives when submerged in a fluid is known as the buoyant force. The fluid exerts this force, which is equivalent to the fluid's weight that the object has displaced. Put another way, the pressure difference between the submerged object's top and bottom causes the buoyant force.

2.Archimedes' Principle: 

The magnitude of the buoyant force acting on an object is equal to the weight of the fluid displaced by that object.

Mathematically, it can be expressed as:

• F (buoyant)= 

Weight of displaced fluid=

ρ fluid×g×V displaced

Where;

• F( buoyant) is the buoyant force,

• ρ( fluid) is the density of the fluid,

• g is the acceleration due to gravity, 

and

• V (displaced) is the volume of fluid displaced by the object.

3.Floating and Sinking: 

According to Archimedes' Principle, an object's density in relation to the fluid's density determines whether it will float, sink, or remain suspended in the fluid.

• The object will float if its density is less than    that of the fluid  

   (buoyant force > object weight).

• The object will stay suspended if its density     and that of the fluid are equal

   (buoyant force = object weight)

• The object will sink if it's density is higher than that of the fluid

    (buoyant force < object weight)

4. Application:

  Many practical uses of the buoyancy law can be found in a variety of industries, such as shipbuilding (creating floatable ships), aerodynamics (designing aircraft and buoyancy in gases), and engineering (building flotation devices and submarines)

All things considered, the buoyancy law is an important idea that aids in our comprehension of why certain items float or sink in liquids and is important when creating objects that interact with fluids.

 

NEWTON'S LAW'S OF MOTION

 1. 

Newton's First Law (Law of Inertia):

 This law states that an object will remain at rest or in uniform motion in a straight line unless acted upon by an external force. In simpler terms, objects tend to keep doing what they're already doing unless something pushes or pulls on them.

2.

Newton's Second Law (Law of Acceleration): This law relates the force acting on an object, its mass, and its acceleration.

 It can be mathematically expressed as -

F=ma, where 

F is the force applied, 

m is the mass of the object, and 

a   is its acceleration. This law essentially explains how objects accelerate when a force is applied to them.

3.

Newton's Third Law (Action-Reaction Law): 

This law states that for every action, there is an equal and opposite reaction. When one object exerts a force on a second object, the second object simultaneously exerts a force equal in magnitude and opposite in direction on the first object. This law is often paraphrased as "for every action, there is an equal and opposite reaction."

STRUCTURAL ANALYSIS – TRIBUTARY AREAS

 1. The tributary is an unloaded area. This statement is:-

a) True

b) False

Explanation: The tributary area is the loaded area of a particular structure directly contributing to the load applied.

2. The tributary area lines between two columns/beams are at how much distance from one of the beam?

a) 0.2 of the total in between length

b) 0.4 of the total in between length

c) 0.5 of the total in between length

d) Depends on the amount of load carried

Explanation: Tributary area is bounded by lines lying halfway from next beam/column, irrespective of load carried.

3. For an interior girder, what is the shape of tributary area?

a) Rectangular

b) Triangular

c) Circular

d) Depends upon case

Explanation: If the girder surrounding the girder in question is similar to it, then it will be a triangle, otherwise it might be trapezium in some cases. 

4. What is the maximum no. of structures to which an area can be a tributary are to?
a) 1
b) 2
c) 3
d) 4

Explanation: A particular area can’t be a tributary area to more than one member of a structure at one time.

5. Which out of the following statements is true?
a) Tributary area > influence area
b) Tributary area <= influence area
c) Tributary area >= influence area
d) No relation can be defined

Explanation: An influence area is always a tributary area. So, tributary area <= influence area.

6. If in an interior beam, adjacent structures are exactly similar then the tributary area is:
a) Trapezium
b) Acute triangle
c) Obtuse triangle
d) Right angled triangle

Explanation: Since, the structures are similar; angles of triangle will be 45 and 90 degrees.

7. One area can serve as an influence area to more than one member of a structure at the same time.
State whether the above statement is true or false.
a) True
b) False

Explanation: Unlike tributary areas influences can serve to more than one as they can affect more than one forces on loaded.

8. When column supports the top floor of a building, then live load reduction is:-

a) Permitted
b) Not permitted
c) Depends upon type of beam
d) Depends upon amount of load 

Explanation: When column support a floor, it should be thought of as supporting a single floor only.

Technical Questions for civil engineer

1.What is the minimum CBR of subgrade   soil ?

As per IRC 58-2015 Clause 5.7.3.6 , a minimum CBR of 8 % is recommended for 500 mm of selected soil used as subgrade.

2. What is code reference from which you are performing CBR test with 3 energy level as per MORTH 5 revision ?

AASHTO Designation: T 193-99 -2003

3. What is the limit of Air Voids , flow & VFB in Dense Bituminous Macadam mix design ?

The limit of Air voids , flow & VFB is 3 -5% , 2- 4 mm & 65-75% simultaneously.

4.What should be the minimum required density of Subgrade soil as per MORT&H 5th revision ?

17.5 KN/m³ or 1.78 gm /cc

5.What is the softening point of VG 30 & VG40 grade bitumen ?

The softening point of VG30/VG 40 grade bitumen is 47 ºC / 50ºC

6.What will be the maximum allowable size of granular material for subgrade soil as per MORT&H specification ?

Allowable size of granular material in subgrade is 50 mm

7.What is the maximum Liquid Limit & Plasticity Index allowed in earth work in embankment/subgrade soil ?

Clay should have Liquid Limit less than 50 % & PI should always be less than 25 %.

8.What is the frequency of taking core for BM/DBM/BC for checking of compaction & thickness of laid layer as per MORT&H 5th revision ?

One core at 700 m²

9.What is the maximum Aggregate Impact Value of aggregate allowed for Bituminous concrete(BC) work in flexible pavement ?

AIV should not be more than 24%.

10.What is the minimum cement content & maximum W/C ratio for M 25 RCC concrete for moderate condition as per MORT&H 5TH Revision ?

Minimum Cement Content 340 Kg & Maximum W/C ratio is 0.45

11.What is the density frequency of compacted layer in Embankment & subgrade/Shoulder ?

1 set of 10 test for 3000 m² of Embankment / 1 set of10 test for 2000 m² of Subgrade/Shoulder.

12.What is difference between Specific Gravity & Density ?

Bulk density is the ratio between soil weight to the total volume of the soil but Specific Gravity (G) is the ratio of the weight in air of a given volume of soil solids at a stated temperature to the weight in air of an equal volume of distilled water at that temperature . Specific gravity has no unit and it is generally used in design of concrete/bituminous mix.

13.What is the maximum Aggregate Impact Value of aggregate for concrete work ?

45%

14.What is the rate of spray of Prime Coat over WMM ?

0.7 -1.0 kg/m²

15.Which IS code specified the specification of aggregates ?

IS 383-2016

16.How much Kinetic Viscosity of VG 40 bitumen is ?

The Kinematic Viscosity of VG 40 grade bitumen is 400 cst minimum at 135 º C

17.What is the dry density of WMM & GSB material in your project ?

The density of WMM/GSB in our project is 2.23 /2.24 gm/cc

18.What is the minimum cement content & maximum W/C ratio for Pile concrete as per IRC 78 -2014 Cl 709.1.9 ?

 Minimum amount of cement content 400 kg/m³ & maximum W/C ratio is 0.40

19. What will be the minimum cement content as per IRC SP 49 2014 for DLC mix design ?

140 kg / m³

20.How many samples you take for 900 m² of DLC laying ?

3 samples (9 Cubes)

What is the Nominal size of aggregate for grade 1 Bituminous Concrete?

19 mm

What is the maximum limit of FI+EI for Dense Bituminous Macadam as per MORT& H 5th revision ?

Maximum FI+EI limit is 35%

What is setting time RS1 & SS1 Emulsion?

15 to 30 minutes for RS1 & 24 hours for SS1  

How many cube mould required for 110 m³ concrete ?

4 +1+1=6 samples means 18 cubes as IS 456-2000

As per MORT&H 5th revision how many grades of GSB are there?

Six grades are there.

BUILDING MATERIALS MCQ

1.  Construction of cavity walls as external walls to protect the building from the outside heat or cold as the hollow space between two walls act as an _______

a) Burning material

b) Insulating material

c) Destructive material
d) Building material

Solution: Properly insulated building cuts down the cost of electric burning in summer as well as in winter. Cavity walls are one of the types of thermal insulation which consists of two walls with cavity in between them.

2.__________ in a building means the free passage of clean air in a building.

a) Habitation

b) Protection

c) Sanitation
d) Ventilation

solution: Ventilation is essential in every building. Due to this, is control dust and other impurities entering in building. 

3. The termite, which are responsible for the destruction of wooden materials, are popularly known as _______

a) Red ants

b) White ants

c) Black ants
d) Big ants

solution: More than 2300 species are living ,only 4% are living in colony . The termites live in a colony and they are very fast in eating wooden and other cellulosic materials as food.

4. The treatment given to the roof of a building to prevent the roof from the leakage of water is known as _________

a) Fire proofing

b) Damp proofing

c) Termite proofing

d) Sound proofing

solution: One of the basic requirements in case of all the buildings is that the structural should remain dry as far as possible. If this condition is not satisfied, it is likely that the building may become inhabitable and hence damp proofing or water proofing is required.

MCQ of Building material:

1. Excess of alumina in brick earth makes the brick 

(A) Impermeable

(B) Brittle and weak 

(C) To lose cohesion 

(D) To crack and warp on drying

2.Inner part of a timber log surrounding the pitch, is called 

(A) Sapwood 

(B) Cambium layer 

(C) Heart wood 

(D) None to these 

3. For testing compressive and tensile strength of cement, the cement mortar is made by mixing cement and standard sand in the proportions of 

(A) 1 : 2 

(B) 1 : 3 

(C) 1 : 4 

(D) 1 : 6 

Types of shallow Foundations:

Spread Footing: The spread footings are those which spread the super-imposed load of the structure over a large area.

The spread footings may be of the following types:-

(a) Single footing for a column,

(b) stepped footing for a column,

(c) sloped footing for a column,

(d) wall footing with steps and without steps, 

(e) Grillage foundation.

Combined Footing:- The common footing which is constructed for two or more columns, is called combined footing.

It may be rectangular or trapezoidal shape of a combined footing.

Strap Footing:- When two or more footings are connected by a beam, it is called a strap footing.

Raft or mat foundation:- A foundation consisting of thick reinforced concrete slab covering the entire area of the bottom of the structure, is known as raft or mat foundation.