Quiz: Mechanical Engineering 24th June

Quiz: Mechanical Engineering
Exam: AE/JE
Topic: Miscellaneous

Each question carries 1 mark
Negative marking: 1/4 mark
Time: 10 Minutes

Q1. What is the pressure inside a soap bubble, over the atmospheric pressure if its diameter is 2 cm and the surface tension is 0.1 N/m.
(a) 0.4 N/m^2
(b) 4.0 N/m^2
(c) 40.0 N/m^2
(d) 400.0 N/m^2

Q2. The general relationship between shear stress (τ) and velocity gradient (du/dy) for a fluid can be written as
τ=A〖(du/dy)〗^n+B
If n<1, B=0
Then the fluid known as
(a) Bingham plastic
(b) Dilatant fluid
(c) Pseudo plastic
(d) Newtonian fluid

Q3. Consider the following statements:
Gases are considered incompressible when Mach number is less than 0.2
A Newtonian fluid is incompressible and non-viscous
An ideal fluid has negligible surface tension
Which of the above statement(s) is/are correct?
(a) 2 and 3
(b) 2 alone
(c) 1 alone
(d) 1 and 3

Q4. Select the correct statement:
(a) local atmospheric pressure depends only upon the height of locally above mean sea level.
(b) local atmospheric pressure is always below the standard atmospheric pressure.
(c) standard atmospheric pressure is the mean local atmospheric pressure at sea level.
(d) a barometer reads the difference between local and standard atmospheric pressure

Q5. Fatigue consideration plays an important role in the design of all of the following components, except
(a) Bridges
(b) Keys
(c) Springs
(d) Gears

Q6. Increase of actual stress over nominal stress due to stress raising notches in fatigue loading is given by
(a) K_f σ_0
(b) K_t σ_0
(c) (K_f-1)σ_0
(d) (K_t-1)σ_0

Q7. Sigma comparator is a type of comparator:
(a) Optical
(b) Electrical
(c) Mechanical
(d) Electronic

Q8. Which of the following fits comes under the category of interference fit?
(a) Tight fit
(b) Push fit
(c) Force fit
(d) Shrink fit

Q9. Cellular manufacturing is suitable for
(a) a single product in large volume
(b) one-off production of several varieties
(c) products with similar features made in batches
(d) large variety of products in large volumes

10. Routing and scheduling are integral part of
    (a) product planning
    (b) work study
    (c) job analysis
    (d) quality control

Solutions
S1. Ans (c)
Sol. Given,
Surface tension (σ)=0.1 N/m
Diameter of soap bubble (d)=2 cm or 0.02 m
We know that
Pressure inside a soap bubble over atmospheric pressure (∆P)=8σ/d=(8×0.1)/0.02
=40.0 N/m^2

S2. Ans (c)
Sol. If n<1, B=0 in τ=A〖(du/dy)〗^n+B
Then, viscosity of fluid will decrease with increase in shear strain rate. This is called Pseudo-plastic fluids. So, it is also called shear-thinning fluid. E.g. blood, milk etc.

S3. Ans (d)
Sol. Gases are considered when Mach number is less than 0.3. So, statement 1 is also true for incompressible fluid. A Newtonian fluid is viscous but incompressible and shear stress is directly (or linearly) proportional to shear strain rate. For an ideal fluid, it should be inviscid, incompressible and should have zero surface tension.

S4. Ans (c)
Sol. Standard atmospheric pressure is the mean-local atmospheric pressure at sea level. It is 101.32 KPa.

S5. Ans (b)
Sol. Key is the weakest portion of a machine assembly and it is not designed for fatigue loading consideration.

S6. Ans (c)
Sol. We know that
Nominal stress =σ0 If K_f is fatigue stress concentration factor then Actual stress due to notch=K(f ).σ0 So, Increase over nominal stress due to notch=(K(f )-1).σ_0

S7. Ans (c)
Sol. Sigma Comparator is a type of mechanical comparator.

S8. Ans (c)
Sol. Force fit is also called interference fit. Transition fit is also called push fit.

S9. Ans (c)
Sol. Group technology is a theory of management based on the principle that “similar things should be done similarly”. It can be applied to various administrative activities including activities involved in manufacturing. Cellular manufacturing uses the principle of group technology by grouping parts with similar characteristics into part-families and corresponding machines into machine cells in order to achieve higher production efficiency compared to traditional manufacturing. Cellular manufacturing is an integral part of lean manufacturing.

S10. Ans (a)
Sol. Routing and scheduling is an integral part of product planning.

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