ISRO Mechanical Questions 2020 | ISRO ME Set-C with Solutions

## Question 1:

A mass of 1 kg of air at 27°C and 0.98 atm is taken through a diesel cycle. If the compression ratio

of the engine is 16, calculate the temperature of the air after compression? (for calculation, take the ratio of specific heats of air as 1.5)

(a) 1200 deg C

(b) 1473 deg C

(c) 927 deg C

(d) 768 deg C

Ans: (c)

## Question 2:

An aircraft is in its take off roll at sea level with ambient temperature of 18°C. What is the

approximate speed of the aircraft if the temperature measured by a probe at the exit of the engine

diffuser is 36°C? (Assuming air stagnation at diffuser outlet and Cp of air as 1.0 kJ/kg.K)

(a) 12 m/s

(b) 3 m/s

(c) 6 m/s

(d) 18 m/s

Ans:

## Question 3:

The external surface of a wall of 3 m height, 5 m width and 0.5 m thickness is at a temperature of

2°C. If a heat loss of 150 W from the room is measured across the wall, find the inner wall

temperature? The thermal conductivity of wall material can be taken as 1 W/m.K

(a) 280 K

(b) 285 K

(c) 268 K

(d) 282 K

Ans: (a)

## Question 4:

The typical range of Prandtl number for water is

(a) 0.004-0.300

(b) 0.7-13.7

(c) 50-500

(d) 2000-1000

Ans: (b)

## Question 5:

Analogy between momentum and heat transfer is known as

(a) Stanton-Prandtl analogy

(b) Grassoff-Meyer analogy

(c) Chilton-Colburn analogy

(d) None of the above

Ans: (c)

## Question 6:

The laws of adhesive wear, commonly referred to as Archard’s law can be expressed as ______. (If ‘Q’ is the total volume of wear debris produced, ‘W’ is the normal load, ‘L’ is the sliding distance, ‘H’ is the hardness of the softest contacting surfaces being worn away, and ‘k’ is a nondimensional wear coefficient dependent on the materials in contact and their exact degree of cleanliness)

(a) Q = kWL/H

(b) Q = kW/LH

(c) Q = kHW/L (d) Q = k/LWH 06.

Ans: (a)

## Question 7:

In a four-bar linkage if ‘S’ is the length of the shortest link, ‘L’ is the length of longest link and ‘P’ & ‘Q’ are length of other links, then the criteria for getting a triple rocker mechanism in which no links will fully rotate is.

(a) S + Q > P + L

(b) S + L < P + Q

(c) S + L = P + Q

(d) S + L > P + Q

Ans: (d)

## Question 8:

The piston of an engine moves with simple harmonic motion. The crank rotates at 120 r.p.m with a stroke of 2 meters. The velocity of the piston, when it is at a distance of 0.8 metre from the center is.

(a) 4.8 π

(b) 2.4 π

(c) 1.2 π

(d) 0.6 π

Ans: (b)

## Question 9:

If a block slides outward on a link at a uniform rate of 30 m/s, while the link is rotating at a constant angular velocity of 50 rad/s counter clockwise, the Coriolis component of acceleration is ______ m/s2 .

(a) 1000

(b) 1500

(c) 3000

(d) 4500

Ans: (c)

## Question 10:

In a screw jack of lead angle α, the effort required to lift the load W is given by ______________ (φ = Friction Angle)

(a) P = Wtan(α – φ)

(b) P = Wtan(α + φ)

(c) P = Wcos(α – φ)

(d) P = Wcos(α + φ)

10. Ans: (b)

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