NHPC JE'21 ME: Daily Practices Quiz. 04-Oct-2021

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NHPC-JE’21 ME: Daily Practices Quiz

NHPC-JE’21 ME: Daily Practices Quiz 04-Oct-2021

Quiz: Mechanical Engineering
Exam: NHPC JE
Topic: Miscellaneous

Each question carries 1 mark
Negative marking: 1/4 mark
Time: 6 Minutes

Q1. The dimension of kinetic energy correction factor α is
(a) M^0 LT^0
(b) M^0 L^1 T^(-2)
(c) M^0 L^0 T^0
(d) M^1 L^2 T^(-2)

Q2. At critical depth of flow
(a) The Froud’s number has a unit value
(b) The specific energy is maximum for a given discharge
(c) The discharge is minimum
(d) The discharge is maximum

Q3. If Nusselt number is 2000 with corresponding Reynolds and Prandtl numbers as 20 and 10 respectively, the relevant Stanton number will be
(a) 40
(b) 20
(c) 5
(d) 10

Q4. The cone clutches have become obsolete because of
(a) Small cone angles
(b) Exposure to dirt and dust
(c) Difficulty in disengaging
(d) All of the above

Q5. The co-ordination number of FCC crystal structure is
(a) 8
(b) 16
(c) 12
(d) 10

Q6. Which one of the following pairs of axis lengths (a, b, c) and inter axial angles (α,β,γ) represents the tetragonal crystal system?
(a) a=b=c and α=β=γ=90°
(b) a=b≠c and α=β=γ=90°
(c) a≠b≠c and α=β=γ=90°
(d) a=b=c and α=β=γ≠90°

Solutions

S1. Ans (c)
Sol. We know that
Kinetic energy correction factor (∝) = (K.E.based on actual velociy )/( K.E.based on Ideal velocity )
▭(∝ = (∫▒〖u^3 dA〗)/Av³).
As dimensions of numerator and denominator are same so, we can say that kinetic energy
correction factor (∝) is dimensionless or its dimension is M^0 L^0 T^0.

S2. Ans (a)
Sol. The Froude Number is a dimensionless parameter used in connection with open channel flow. For Fr < 1, flow is sub-critical; for Fr = 1, flow is critical and for Fr > 1, flow is supercritical

S3. Ans. (d)
Sol. we know that, the Stanton number is
Stanton number = (Nusselt number)/(Reynolds number ×prandtl number)
Stanton number = 2000/(20 × 10)
Stanton number = 10

S4. Ans (a)
Sol. For designing plate or disc clutch, we assume uniform wear theory because most of the clutches wear uniformly for most of their life cycle. Hence, designing of a clutch by considering uniform wear theory, will be cost effective and close to real life simulation of clutch.

S5. Ans (c)
Sol.
Crystal structure Co-ordination number
1. SC 6
2. BCC 8
3. FCC 12
4. HCP 12

S6. Ans (b)
Sol.
Tetragonal Crystal system is shown in figure which depicts that
a=b≠c and α=β=γ=90°