Quiz: Mechanical Engineering

Exam: AE/JE

Topic: Miscellaneous

Each question carries 1 mark

Negative marking: 1/4 mark

Time: 10 Minutes

Q1. What can be the maximum displacement amplitude for an instrument having natural frequency of 20 rad/sec and withstand capability of 4 m/s²

(a) 0.001 m

(b) 0.01 m

(c) 0.1 m

(d) 0.5 m

Q2. Which of the following purposes is served by critical damping?

(a) It provides basis of determining critical damping.

(b) It predicts nature of vibration

(c) It provides a measure of the relative amount of damping in a system.

(d) It enables measurement of damping.

Q3. Which of the following equilibrium equations should be satisfied by the joints in truss: –

(a) ΣH=0

(b) ΣH=0,ΣV=0

(c) ΣV=0

(d) ΣH=0,ΣV=0,ΣM=0

Q4. A motor car moving at a certain speed takes a left turn in a curved path. If the engine rotates in the same direction as that of wheels, then due to the centrifugal forces

(a) the reaction on the inner wheels increases and on the outer wheels decrease

(b) the reaction on the outer wheels increases and on the inner wheels decrease

(c) the reaction on the front wheels increases and on the rear wheels decrease

(d) the reaction on the rear wheel increase and on the front wheel decrease

Q5. Young’s modulus is defined as the ratio of

(a) volumetric stress and volumetric strain

(b) lateral stress and lateral strain

(c) longitudinal stress and longitudinal strain

(d) longitudinal stress and longitudinal strain

Q6. Match the following List-I (Material) with List-II (Poisson’s ratio):

List-I

A. Rubber

B. Brass

C. Grey cast iron

D. Steel

List-II

- 0.25
- 0.45-0.50
- 0.27-0.30
- 0.34

Codes:

A B C D

(a) 2 4 1 3

(b) 3 1 4 2

(c) 2 1 4 3

(d) 3 4 1 2

Q7. During a tensile test on a specimen of 1 cm^2 cross-section, maximum load observed was 100 kN and area of cross-section at neck was 0.5 cm^2. UTS of specimen is

(a) 400 MPa

(b) 1000 MPa

(c) 1600 MPa

(d) 2000 MPa

Q8. Plasticity must be considered in designing for processes except

(a) Autofrettage

(b) Shrink fitting

(c) Rotating shaft

(d) Over-speeding of rotor disk

Q9. Figure shows a four-bar chain and the number indicates the respective link lengths in cm. The type of the mechanism is known as

(a) slider crank

(b) double crank

(c) crank rocker

(d) double rocker

Q10. A slider sliding at 10 cm/s on a link which is rotating at 60 rpm is subjected to Coriolis acceleration of magnitude, in cm/s².

(a) 20π

(b) 10π

(c) 40π

(d) 90π

Solution

S1. Ans.(b)

Sol. given, natural frequency, ω_n=20 rad\/s

Withstand capability or maximum acceleration (a) = 4

Amplitude (δ)= ?

For SHM,

Withstand capability (a) = δω_n^2

δ=4/400

δ=0.01 m

S2. Ans.(b)

Sol. for critical damping ▭(ς=1)

It is used to predicts the nature of vibration.

S3. Ans (b)

Sol. As we know that no bending moment acts on the joints in a truss, only horizontal and vertical component of forces should be zero for equilibrium.

S4. Ans (b)

Sol. As motor car will try to go outward due to centrifugal force then more pressure is exerted on the outer wheels as compared to the inner wheels.

S5. Ans (d)

Sol. Young’s modulus is defined as the ratio of longitudinal stress and longitudinal strain.

i.e. 𝐸=𝜎𝜀

S6. Ans (a)

Sol. Poisson’s ratio for the following material will be as given below-

A. Rubber 0.45−0.5

B. Brass 0.34

C. Grey cast iron 0.25

D. Steel 0.27−0.3

S7. Ans (b)

Sol.

We know that UTS of specimen=(maximum load observed)/(original cross-section area of specimen)

UTS=(100×10^3)/(1×10^(-4) )

UTS=1000 MPa

S8. Ans (c)

Sol. Chances of plastic deformation is negligible for a rotating shaft if the system is balanced.

S9. Ans.(b)

Sol. Given,

S=5

l=10

p=8

q=9

s+l =15

p+q=18

Hence, s+l<p+q

And shortest link is fixed.

So, according to Grashoff’s inequality or law this is a double- crank mechanism,

S10. Ans.(c)

Sol.

we know that,

Coriolis acceleration a_c=2wv —————— (1)

w=2πN/60

=(2π×60)/60=2π rad/s

V = 10 cm/s

a_c=2wv

=2×2π×10

▭(a_c=40π cm\/s^2 )