RRB JE ME (CBT II) Mock Test- 3 - Mechanical Engineering MCQ

1. Pack method

2. Cyaniding

3. Nitriding

4. Induction Hardening

5. Flame hardening

Important Points

Heat treatment is an operation involving heating and cooling of a metal or alloy so as to obtain the ,,certain desirable properties. A few important heat treatment processes are:

1. Annealing

2. Normalising

3. Hardening

4. Tempering

Concept:

Time of flight: t =

Maximum height: H =

Horizontal Range: R =

When θ = 45°: R_max =

The range of a projectile is maximum, when the angle of projection is 45°.

Calculation:

R_max = R/sin2θ = 15 / sin30^o = 3 km

Coating factor: The ratio of the coating diameter to the core wire diameter is called the coating factor.

• 1.25 to 1.3 for light coated

• 1.4 to 1.5 for medium coated

• 1.6 to 2.2 for heavy coated

• Above 2.2 for super heavy coated electrodes

Reynold Number

Where U is the average stream velocity and L is the characteristics length/width.

The hydraulic diameter which is used as the characteristic length in determination of friction factor, instead of ordinary geometrical diameter, is defined as

where A_w is the flow area and P_w is the wetted perimeter

Circular pipe of diameter d:

Important Points

Square duct of size a:

The rectangular duct of size a × b:

Concept:

The PERT (Project Evaluation and Review Technique) technique is used, when activity time estimates are stochastic in nature. For each activity, three values of time (optimistic, most likely, pessimistic) are estimated.

• Optimistic time (to) estimate is the shortest possible time required for the completion of the activity.
• The most likely time (tm) estimate is the time required for the completion of activity under normal circumstances.
• Pessimistic time (tp) estimate is the longest possible time required for the completion of the activity.

In PERT expected time of an activity is determined by using the below given formula:

Variance, σ2 =

Calculation:

From detritus, the chain proceeds to detritivores, then to carnivores, and finally to top carnivores.

We are aware that normally rainwater has a pH of 5.6. When the pH of the rainwater drops below 5.6, it is called acid rain.

Acid rain refers to the ways in which acid from the atmosphere is deposited on the earth’s surface. Oxides of nitrogen and sulphur which are acidic in nature can be blown by the wind along with solid particles in the atmosphere and finally settle down either on the ground as dry deposition or in water, fog and snow as wet deposition.

Acid rain is a byproduct of a variety of human activities that emit the oxides of sulphur and nitrogen in the atmosphere. As mentioned earlier, burning of fossil fuels (which contain sulphur and nitrogenous matter) such as coal and oil in power stations and furnaces or petrol and diesel in motor engines produce sulphur dioxide and nitrogen oxides.

SO₂ and NO₂ after oxidation and reaction with water are major contributors to acid rain because polluted air usually contains particulate matter that catalyses the oxidation.

2SO₂ (g) + O₂ (g) + 2H₂O (l) → 2H₂SO₄ (aq)

4NO₂ (g) + O₂ (g)+ 2H₂O (l) → 4HNO₃ (aq)

The bad effects of acid rain

• When acid rain falls and flows as groundwater to reach rivers, lakes etc, it affects plants and animal life in the aquatic ecosystem

• Acid rain is harmful to agriculture, trees,.. and plants as it dissolves and washes away nutrients needed for their growth.

• It causes respiratory ailments in human beings and animal

• It may also cause corrosion in many buildings bridges, monuments, fencing etc

• It causes irritation in the eyes and skin of human beings

• This rain reduces the lustre of the metals too

• Acid rain damages buildings and other structures made of stone or metal

• The Taj Mahal in India has been affected by acid rain

Important Points:

• The prescribed permissible noise level for silence zones is 50 and 40 decibels during daytime and night-time respectively

• The prescribed permissible noise level for the industrial area is 75 and 70 decibels during daytime and night-time respectively

• The prescribed permissible noise level for the residential area is 55 and 45 decibels during daytime and night-time respectively

• Delhi is the only union territory of India which has its own High court.

• It was established on 31 October 1966.

• The High Court of Delhi was established with Chief Justice KS Hegde, Justice ID Dua, Justice HR Khanna and Justice SK Kapur as the 4 judges.

• Chandigarh comes under the jurisdiction of Punjab and Haryana High Court.

• Puducherry comes under the jurisdiction of Madras High Court.

• Daman and Diu come under the jurisdiction of Bombay High Court.

• With the exit of Viral Acharya, the RBI rejigged portfolios of the other three deputy governors giving the important monetary policy and forecasting department to B P Kanungo.

• Now, all the other 3 deputy governors -- N S Vishwanathan, B P Kanungo and M K Jain have been made responsible for 12 departments each.

• Viral Acharya resigned in June 2019 as the deputy Governor of RBI.

The Result of a non-concurrent force system is the one which will have the same rotational and translatory effect as the given system of forces. It may be a single force, a pure moment of a force and a moment.

When a body is acted upon by a number of coplanar non-concurrent forces. A little consideration will show, that as a result of these forces, the body may have any one of the following states:

1. The body may move in any one direction.

2. The body may rotate about itself without moving.

3. The body may move in any one direction and at the same time, it may also rotate about itself.

4. The body may be completely at rest.

For Equilibrium of coplanar non-concurrent force system:

ΣF_x = 0

ΣF_y = 0

ΣM = 0

Municipal solid waste:

• Municipal solid waste (MSW) is more commonly known as trash or garbage

• It consists of everyday items we use and then throw away, such as product packaging, grass clippings, furniture, clothing, bottles, food scraps, newspapers, appliances, paint, and batteries.

• It is the non-hazardous solid waste

• It comes from our homes, schools, hospitals, and local councils

Important points:

There are different methods of solid waste management. The following are some of the recognized methods:

• Sanitary landfill

• Incineration

• Recovery and Recycling

• Composting

• The Dead Sea is a salt lake which is bordered by Jordan to the east and Israel to the west.

• The Dead Sea lies in the Jordan Rift Valley, with the Jordan River as its main tributary.

• Its surface and shores are 430.5 meters (1412 feet) below sea level.

Light rays from infinity, parallel to the principal axis, thus meet at the point on the principal axis on the side of the mirror, which is towards the object.

This distance is considered as negative.

Hence the focal length of a concave mirror is negative.

⇒ Focal length, f = R/2

⇒ f = 30/2 = 15 cm

For the Concave mirror, the focal length is negative.

Therefore, f = -15 cm.

KE gained = mgh

KE gained = 8*10*20

KE gained = 1600 J

KE = (1/2)mv²

1600 = (1/2)*8*v²

Solve for v

V = Square root of 400

V = 20 m/s²

The atmospheric refraction occurs in a medium of gradually changing refractive index.

Since the atmosphere bends starlight towards the normal, the apparent position of the star is slightly different from its actual position.

Most metal oxides are insoluble in water but some of these dissolve in water to form alkalis.

Sodium oxide and potassium oxide dissolve in water to produce alkalis as follows

Na₂O(s) + H₂O(l) → 2NaOH(aq)

K₂O(s) + H₂O(l) → 2KOH(aq)

Non-Metallic Oxides:

Most non-metals produce acidic oxides when dissolved in water

CO₂ + H₂O → H₂CO₃ (Carbonic acid)

SO­₃ + H₂O → H₂SO₄ (Sulphuric acid)

Edging: This applied to increase the cross-sectional area of the stock at the expense of its length.

Steel is an alloy of iron and carbon with a carbon content of up to a maximum of 2%.

Stainless steel contains Iron, Carbon, Chromium, and Nickel.

Stainless steels typically contain 10 - 30 % chromium besides other elements like C, Mn, Si, S, etc. Chromium imparts corrosion resistance to steel. Varying amounts of other alloying elements like Ni, Mo, V, Ti, Ni, etc., may be added to obtain certain specific properties.

According to Newton’s Second Law

The rate of change of momentum of an object is directly proportional to the resultant force applied and is in the direction of the resultant force.

Δ(mv) = F × Δt = 20 × 1 = 20 kg m/s

So, the longest path will represent the critical path for the network, and it will represent the minimum possible duration required to complete the project.

The critical path will be the longest path in the network requiring the maximum amount of time, but it will represent the minimum duration that is required to complete all the activities i.e. completion of a project.

• The internet is a globally connected network system that transmits data via various types of media. Sometimes it is referred to as a ‘network of networks’

• The World Wide Web, or simply the web, is a way of accessing information over the medium of the internet.

• A web browser is a software application for accessing the information on the World Wide Web.

When a body is loaded within an elastic limit, it changes its dimensions and on the removal of the load, it regains its original dimensions. So long as it remains loaded, it has stored energy in itself. On removing the load, the energy stored is given off, as in the case of a spring. This energy, which is absorbed in a body when strained within the elastic limit, is known as strain energy.

The strain energy stored in a body due to external loading, within the elastic limit, is known as resilience. The maximum energy stored in a body up to the elastic limit is called proof resilience.

The proof of resilience per unit volume of a material is known as the modulus of resilience.

Strain energy stored in a body due to tensile or compressive load or resilience:

Modulus of resilience:

Ductility is a measure of a material's ability to undergo significant plastic deformation before rupture, which may be expressed as percent elongation or percent area reduction from a tensile test.

In fatigue testing, the endurance limit i.e. the maximum stress which can be applied to a material for an infinite number of stress cycles without resulting in failure of the material is applied and measured.

Hardness is a characteristic of a material, not a fundamental physical property. It is defined as the resistance to indentation, and it is determined by measuring the permanent depth of the indentation. Hardness test is used to determine resistance to penetration.

A. Ductility ⇒ III. Tension Test

B. Endurance limit ⇒ II. Fatigue Test

C. Toughness ⇒ I. Impact Test

D. Resistance to penetration ⇒ IV. Hardness Test

• Kudremukh National park is located in Chikkamagaluru district of Karnataka.

• It was declared as a National Park in 1987.

• Other famous National parks in Karnataka are Bandipur, Nagarhole, and Anshi National Park.

• Famous National Parks in Kerala are Periyar, Silent Valley, and Anamudi Shola National Park.

• Famous National Parks in Tamil Nadu are Mudumalai, Mukurthi, and Indira Gandhi National Park.

• Famous National Parks in Odisha are Simlipal, and Bhitarkanika National park.

The temperature at which the structure of steel completely changes to AUSTENITE is called the upper critical temperature. This varies depending on the percentage of carbon in the steel.

• 0.57% and 1.15% carbon steel: In these cases, the lower critical temperature is 723°C and the upper critical temperature is 800°C.

• For 0.84% carbon steel, both lower critical temperature and upper critical temperature are 723°C. This steel is called eutectoid steel.

If steel is heated, a change in its structure commences from 723°C. The new structure formed is called ‘AUSTENITE’. Austenite is non-magnetic.

• If the hot steel is cooled slowly, the old structure is retained and it will have fine grains which makes it easily machinable.

• If the hot steel is cooled rapidly the austenite changes into a new structure called ‘MARTENSITE’. This structure is very fine-grained, very hard and magnetic. It is extremely wear-resistant and can cut other metals.

Methods of honing: Manual stroking and Power stroking

Manual stroking

• Manual stroking is preferred for large quantities when tolerances are extremely close.

• Many operators prefer this because of the flexibility in operation.

• This eliminates the use of expensive fixtures to hold the work.

• Jobs can be quickly changed from one type to another. Jobs can be reversed from end to end for accurate honing and correction.

• The stroke length can be altered depending on the actual requirement of the individual workpiece.

Power stroking

• Power stroking is used for honing all types of workpieces. Power stroking may prove to be economical particularly in the case of small parts.

Note

• Sometimes for final finishing, manual stroking is employed after power stroking.

Magnifications of 2000 times are quite common, and some may have as high as 40,000.

If a comparator has a magnification of 1000 and if the difference between the standard and actual dimensions of a work piece is 0.02 mm, it will result in pointer movement of 20 mm on the dial or the recording device of the comparator.

• In mechanical comparators, the magnification ranges from about 250 to 5000. These comparators are relatively cheap and are used mainly for comparative measurement of external surfaces.

• With an electrical comparator, magnifications of the order of 40000 or higher are obtainable.

• With a Pneumatic comparator, the magnification factor will vary from 1000 to 5000.