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NHPC JE’21 ME: Daily Practices Quiz. 06-Oct-2021

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NHPC-JE’21 ME: Daily Practices Quiz

NHPC-JE’21 ME: Daily Practices Quiz 06-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. In casting, while designing Gating system, the formula of choke is (A) is
where, m = mass of casting, ρ = density of molten metal, H = effective metal height, ɳ = efficiency factor, t = pouring time
(a) A=m/(ρtɳ √2gH)
(b) A=mρt/(ɳ √2gH)
(c) A=2m/(ρtɳ √2gH)
(d) A=(mtɳ )/(ρ√2gH)

Q4. Which of the following is (are) the casting defect?
(a) Hot spot
(b) Blow holes
(c) Fusion
(d) All of these

Q5. The moment of inertia of a hollow circular section whose external diameter is 13 cm and internal diameter is 12 cm about centroidal axis is _______
(a) 437.5
(b) 137.5
(c) 284.5
(d) 384.1

Q6. Which cross-section of a cantilever beam which is loaded with UDL can give economical design–
(a) Square
(b) Circular
(c) I-Section
(d) Rectangular

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. (a)
Sol. Choke area (A)
A=m/(ρtɳ √2gH)
S4. Ans. (d)
Sol. Casting defects are blow holes, open blow, pin hole porosity, cuts and washes, metal penetration, fusion, runout, misrun and cold shut, slag inclusion hot tear and hot spot.

S5. Ans. (d)
Sol. moment of inertia of follow circular section
I=π/64 ( d_O^4-di_O^4 )
=π/64 (13^4-12^4 )
=384.1 cm^4
S6. Ans. (c)
Sol. I-section of a cantilever beam which is loaded with UDL will give must economical design as for strongest cross section, moment of resistance (M_R) should be maximum, which depend upon section modules (2). For same cross-sectional area, section modules of I-section is maximum, hence it will be most economical design.

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Published by VINAYAK KUMAR

Graduated from BIT Sindri, Postgraduated from IIT BHU Varanasi

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