RCFL MT Mechanical Mock Test - 5 - Mechanical Engineering MCQ

Pressure Angle is the measure of the steepness of the cam profile. The angle between the direction of the follower movement and the normal to the pitch curve at any point is called pressure angle. Pressure angle varies from maximum to minimum during complete rotation.

The pressure should not exceed 30^० in the case of cams with translating followers (and angle should be less than 45^० for low-speed cam mechanisms with oscillating followers).

The area under P-V diagrams represents the work done.

Since the slope of the adiabatic process is greater than the slope of the isothermal process.

On the P-V diagram, Area under adiabatic curve > Area under the isothermal curve.

Work done under an adiabatic process is greater than work done under an isothermal process.

P_n = The component of force P, normal to section FG = P cos θ

P_t = The component of force P, along the surface of the section FG (tangential to the surface FG) = P sin θ

σ_n = Normal Stress across the section FG

σ_n=σcos²θ

σ_t = Tangential/Shear Stress across the section FG

Concept:

P-V-T relationship for an adiabatic process:

The flow rate through a pipe is usually measured by providing a coaxial area contraction within the pipe and by recording the pressure drop across the contraction, which is the application of Bernoulli’s equation.

Three flow meters primarily operate on this principle:

- Venturimeter

- Orificemeter

- Pitot tube

Crystal structure of Material

FCC: - Ni, Cu, Ag, Pt, Au, Pb, Al, Austenite or Ƴ-iron

BCC: - V, Mo, Ta, W, Ferrite or α-iron, δ-ferrite or δ-iron

HCP: - Mg, Zn

Cobalt: - HCP < 420°C, FCC > 420°C

Chromium: - HCP < 20°C, BCC > 20°C

Glass: - Amorphous

An orifice meter provides a simpler and cheaper arrangement for the measurement of flow through a pipe. An orifice meter is essentially a thin circular plate with a sharp-edged concentric circular hole in it.

C_d is defined as the ratio of the actual flow and the ideal flow and is always less than one.

For the orifice meter, the coefficient of discharge C_d depends on the shape of the nozzle, the ratio of pipe to nozzle diameter, and the Reynolds number of the flow.

The efficiency of Carnot engine (η_E) = 50%

η_E=1−TLTH=0.5

Now, this is converted to the heat pump,

Dividing by T_H

Short trick:

If a Carnot heat engine which is operating between two temperature limits is converted to a heat pump, then

Aluminium casting alloys offer a range of advantages, particularly good castability. This includes a relatively high fluidity, low melting point, short casting cycles, relatively low tendency for hot cracking, good as-cast surface finish, and chemical stability.

For pure shear, radius is equal to shear stress and the centre lies on the point of intersection of axes.

Normalizing: Heat the steel from 30°C to 50°C above its upper critical temp, held about fifteen minutes, and then allowed to cool down in still air. The homogeneous structure provides a higher yield point, ultimate tensile strength, and impact strength with lower ductility to steels.

Main objective

1. Refine grain size in metal, improve strength and hardness, reduce ductility

2. Remove cold worked stress.

3. Remove dislocations due to hot working.

Hooke's law states that the force applied to an elastic material is directly proportional to the extension produced. Therefore Hooke's law holds good up to limit of proportionality.

The refrigerators are the heat pumps which are used to lower the temperature of a given volume by doing work on fluid. The refrigerators work on a reverse Carnot cycle. The cool liquid passing through a chamber which is warmer does work on this fluid to convert it into the gaseous form thus lowering the temperature in the chamber. This process continues so as to bring the temperature of the chamber to a required temperature.


The quality or efficiency of performance of a refrigerator is determined by the coefficient of performance (COP) which is the ratio of the heat supplied or the work done by the air in the chamber to the work required by the system.

COP=Q/W

The work done W is the external work provided to the system for this non-spontaneous process to happen, in our case the electrical energy.
The superheating is the process in which the excess amount of heat is provided to the coolant. This increases the rate of cooling, which is a good indicator for COP.
But also, we should understand that if superheating occurs in a refrigerator, the external energy should be greater to keep the cycle moving.
From the above observations, the coolant evaporates faster adding efficiency of the system, on the other hand, the W required by the system increases, which clearly denotes a decline in the efficiency or the coefficient of performance of the refrigerator.
We get to know that the COP either increases or decreases when superheating takes place in a refrigerator, it is not consistent and therefore unpredictable.

Lower pair: When the two elements of a pair have a surface contact when relative motion takes place, and the surface of one element slides over the surface of the other, the pair formed is known as the lower pair. Sliding pairs, turning pairs, and screw pairs are examples of lower pairs.

Higher pair: When the two elements of a pair have a line or point contact when relative motion takes place, and the motion between the two elements is partly turning and partly sliding, then the pair is known as higher pair. A pair of toothed gearing, belt and rope drives, ball and roller bearings, and cam and follower are examples of higher pairs.

In Belt and pulley, due to line contact, they form a higher pair.

In actual compressors, a small clearance is left between the cylinder head and piston to accommodate the valves and to take care of thermal expansion and machining tolerances.

A large clearance volume results in low volumetric efficiency and hence large cylinder dimensions increase the contact area between the piston and cylinder and so, increases friction and work.

Volumetric efficiency is given by:

Where c = Clearance ratio.

P₂/P₁=Pressure;ratio

As the clearance ratio increases, the volumetric efficiency of the reciprocating compressor decreases as the pressure ratio increases.

The idea is to express that it is the first time that Oxford has allowed public to vote. Thus, only ‘history’ is the best fit while ‘course’ and ‘age’ are incorrect.

Hence, the correct answer is option D.

• Meaning of Warrior: A brave or experienced soldier or fighter.
• Meaning of Sailor: a person who goes sailing as a sport or recreation
• Meaning of Pirate: a person who attacks and robs ships at sea
• Meaning of Spy: a person employed by a government or other organization to secretly obtain information on an enemy or competitor

Unconnected not joined together or to something else.
Chaotic : in a state of complete confusion and disorder.
Unaccountable : unable to be explained; Inexplicable.
Confusing : bewildering or perplexing.
Inexplicable : unable to be explained or accounted for.

Synonym of Inexplicable is Unaccountable

The correct order will be:
Since the beginning of history → the Eskimos and Red Indians (Q)→ have managed to catch (P)→ a few specimens of this aquatic animal (S)→ by a very difficult method. (R)

Let the length of bamboo be x metres.
Length of bamboo above water

Total females = 100% - 52% = 48%
So the answer = (100 – 60)% of 52% + (100 – 70)% of 48% = 35.20%
Hence, Option B is correct.

From the common explanation, we get Aarti sits third to the right of Kirti.

Hence, Option D is correct.

Final Arrangement:

Common Explanation:

References:

Eight students Kirti, Ayushi, Manu, Sona, Aarti, Bobby, Ankita and Divya are sitting around the square table.

Four students sit on each side while rest on each corner.

Students at the side face away from the centre and students at the corner faces towards the centre.

Inferences:

So, we need to arrange as follows to accommodate the information as stated in the question,

References:

Divya sits third to the left of Ayushi.

Kirti sits opposite to Manu and both faces away from the centre.

Inferences:

From the above references, we get the following two different cases:

Case 1:

Case 2:

References:

Neither Kirti nor Manu are beside Ayushi.

Sona sits immediate left of Ankita, who sits on the side of the table.

Bobby is not an immediate right of Ayushi.

Bobby is not adjacent to Manu.

Inferences:

So, from this case 2 will be eliminated as neither Kirti nor Manu are beside Ayushi.

Now, from case 1 we get the following final arrangements:

All these are used for broadcast.

Given:

Length of rectangle = 3/5 of radius of circle

Radius of circle = Side of square with area 6400 m2

Breadth of rectangle = 15 m 

Formulas used:

Area of square = (Side)²

Perimeter of rectangle = 2(Length + Breadth) 

Calculation:

Area of square = 6400 m2

⇒ Side² = 6400 

⇒ Side = √6400 = 80 m 

Radius of cirlce = Side of square = 80 m 

⇒ Length of rectangle = 3/5 × 80 = 48 m 

∴ Perimeter of the rectangle = 2(48 + 15) m 

⇒ 126 m 

Given number 7 5 9 3 8 4 6 2

Arrange the digits in ascending order,

Therefore, such pair = six

i.e. (7,9), (5,8), (3,6), (8,6), (5,3) and (4,2).

When the digits of the number '6379452' are arranged in ascending order,
then rearrangement will be 2 3 4 5 6 7 9

Now, fourth digit from the left = 5

Second digit from the right = 7

Sum of fourth and second digit = 5 + 7 = 12

The logic followed here is:

In figure 1:

32 = (2 + 2) × 8

4 × 8

32

In figure 2:

24 = (3 + 1) × 6

4 × 6

24

Similarly,

In figure 3:

45 = (4 + ?) × 5 

4 + ? = 9

? = 9 - 4

? = 5

Hence, the correct answer is "5".

From the common explanation, we get R sits exactly opposite to U.
Hence, Option C is correct.
Final Arrangement:

Common Explanation:
References:
Exactly two persons are sitting between P and Q.
Only one person is sitting between P and U.
Inferences:
From the above references, we get two different cases:

References:
S is sitting second to the right of R.
Inferences:
From the above reference, we get the following arrangements:

References:
T is not sitting beside S.
Inferences:
So, from this case 2 will be eliminated as T is not sitting beside S.
Hence, we get our final arrangement: