 # Quiz: Mechanical Engineering 05 May 2020

Quiz: Mechanical Engineering
Exam: ISRO (TECHNICAL ASST.)
Topic: Miscellaneous

Each question carries 4 mark.
Negative marking: 1 mark
Time: 15 Minute

Q1. The pressure head loss experienced by fluid flow due to friction in a pipe reduces with
(a) increasing length of pipe
(b) increasing diameter of pipe
(c) decreasing length of pipe
(d) both b and c

Q2. Which of the following is correct for a body in simple harmonic motion?
(a) Acceleration is proportional to displacement from mean position
(b) Velocity is minimum at mean position
(c) Acceleration is maximum at mean position
(d) None of these

Q3. Which of the following is true about amount of heat flow in unit time by conduction?
(a) Decreases with increase in area of the body
(b) Increases with increase in area of the body
(c) Increases with increase in thickness of body
(d) Decreases with increase in temperature difference between the faces of the body

Q4. If an unconstrained steel bar is heated uniformly, there develops
(a) Thermal stress
(b) Tensile stress
(c) Compressive stress
(d) No stress

Q5. A rotating fan completes 1200 revolutions per minute. If the tip of the blade is at a radius of 0.7 m, then the blade tip speed is (take π=22/7)
(a) 44 m/s
(b) 22 m/s
(c) 66 m/s
(d) 88 m/s

Q6. Which of the following statements are correct when related to thermodynamic system?
1.Internal energy is a property
2.Internal energy is path independent function
3.Internal energy is path dependent function
4.Internal energy is the area under PV curve.
(a) 1 & 4
(b) 1 & 2
(c) 1 & 3
(d) 2 & 4

Q7. The number of oxygen atoms in 64 grams of Oxygen gas is
(a) 6.023 × 10^23
(b) 12.023 × 10^23
(c) 24.092 × 10^23
(d) 6.023 × 10^27

Q8. Pressure intensity at a point in a fluid at rest is 4 N/cm^2. The corresponding height of water would be (Assume g = 10 m/s^2)
(a) 4 m
(b) 2 m
(c) 0.4 m
(d) 40 m

Q9. Which of the following milling processes is also called conventional milling?
(a) Up-milling
(b) Down-milling
(c) Face-milling
(d) End-milling

Q10. Which of the following thread is used for high power transmission?
(a) Acme
(b) Square
(c) Buttress
(d) Trapezoidal

Solutions

S1. Ans (d)
Sol. We know that pressure head loss in a pipe is given by Darcy-Weisbach’s equation.
h=(fLV^2)/(d.2g)
Here, h decreases with increasing diameter and decreasing length of the pipe.

S2. Ans (a)
Sol. In simple harmonic motion, acceleration of a particle is proportional to the displacement from the mean position.
i.e. Acceleration ∝ -(Displacement)
Acceleration is minimum at the mean position and maximum at the end positions.

S3. Ans (b)
Sol. We know that Fourier’s law of conduction for heat flow rate is given by
Q= -kA(dT/dx)
Q increases with increasing area and temperature difference and Q decreases with increasing thickness of the wall along the heat flow.

S4. Ans (d)
Sol. Stress is defined as internal resistance invoked by a body to the external forces. If there is no external force on the body then there is no stress in it. Hence, in an unconstrained steel bar, there is no stress due to heating.

S5. Ans (d)
Sol. Blade tip speed for a rotor is given by
V=rω …………(1)
Given,
N= 1200 rpm then ω=2πN/60=(2×22×1200)/(60×7)
From equation (1)
V=0.7×(2×22×1200)/(60×7)
V=88 m/s

S6. Ans (b)
Sol. Internal energy is defined by first law of thermodynamics. It is a property of a thermodynamic system. So, it is path-independent function.

S7. Ans (c)
1 mole (or 32 grams) of oxygen gas contains 6.023 × 10^23 molecules, so, 64 grams of oxygen gas contains 12.046 × 10^23 molecules.
1 molecule (or 32 grams) of oxygen gas has 2 mole-atoms, hence 64 grams (or 2 molecules) of oxygen gas has four mole-atoms or 24.092 × 10^23 atoms.

S8. Ans (a)
Sol. We know that
Pressure intensity at a point (P) = ρgh
height of fluid or water (h)=P/(ρg) = (4×10000)/(1000×10)
height of fluid or water (h)=4 m

S9. Ans (a)
Sol. Up-milling is a milling process in which cutter moves in the opposite direction of work-piece motion. It is also called conventional milling process because of its cutter motion opposite to the work-piece.

S10. Ans (b)
Sol. Square thread is used for high power transmission due to its highest efficiency in all other given threads.

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