Quiz: Mechanical Engineering

Exam: AE/JE

Topic: Miscellaneous

Each question carries 1 mark

Negative marking: 1/4 mark

Time: 10 Minutes

Q1. 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.

Q2. Which of the following behaviour of the system defines under-damped harmonic oscillator?

(a) The system returns (exponentially decays) to equilibrium without oscillating

(b) The system returns to equilibrium as quickly as possible without oscillation.

(c) The system oscillates (at reduced frequency compared to the undamped case) with the amplitude gradually decreasing to zero.

(d) The system oscillates at its natural resonant frequency.

Q3. Force F in the given figure equals to

(a) √3 kN

(b) 2 kN

(c) – √3 kN

(d) 3√3 kN

Q4. How can the resultant of two forces P and Q such that P > Q acting along the same straight line, but in opposite direction be given as?

(a) P + Q

(b) P – Q

(c) P/Q

(d) Q/P

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) None of the above

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. Match the following List-I (Kinematic pair) with List-II (Application):

List-I

A. Sliding pair

B. Turning pair

C. Rolling pair

D. Spherical pair

List-II

- Ball and roller bearing
- Rectangular rod in a rectangular hole
- Ball and socket joint
- Circular shaft revolving inside a bearing

Codes:

A B C D

(a) 3 1 4 2

(b) 2 4 1 3

(c) 3 1 2 4

(d) 2 1 4 3

10

Q10. The transmission angle is minimum and maximum respectively, when the crank angle with the fixed link is

(a) 0° and 270°

(b) 90° and 270°

(c) 0° and 180°

(d) 0° and 90°

Solutions

S1. Ans.(b)

Sol. for critical damping ▭(ς=1)

It is used to predicts the nature of vibration.

S2. Ans.(d)

Sol. ς=c/(2mω_n )<1

This condition is known as under-damping, as under damping system does simples harmonic motion.

In underdamped system, amplitude of vibration decreases slowly in exponential manner.

Displacement at any instant of time for under damped system is given by ▭(x=Ae^(- ςω_n t) (sin( ςω_n t)+ϕ) )

S3. Ans.(a)

Fig.

Sol. from lami’s theorem

1/sin150 = F/sin〖60°〗

F = sin〖60°〗/sin〖150°〗

F = √3 N

S4. Ans.(b)

Sol. R = √(P^2+Q^2+2PQ cos) θ

R = √(P^2+Q^2+2PQ cos〖180°〗 )

R = √(P^2+Q^2–2PQ)

R = √((P-Q)²)

R = P – Q

S5. Ans (c)

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

i.e. E=σ/ε

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=(100X〖10〗^3)/(1X〖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. Rectangular rod in a rectangular hole forms a lower pair.

S10. Ans (c)

Sol.

Transmission angle (μ)

→ Angle between coupler link and output link i.e. angle b/w link 3 & 4.

→ It should be greater than 45° for continuous power transmission.

→ for α= 0 or 180°, w_4 becomes zero and MA= ∞ (Toggle position)