NHPC JE’21 ME: Daily Practices Quiz. 07-Oct-2021

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NHPC-JE’21 ME: Daily Practices Quiz

NHPC-JE’21 ME: Daily Practices Quiz 07-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 mechanism, which is an exact straight-line mechanism using lower pairs?
(a) Watt’s mechanism
(b) Grasshopper mechanism
(c) Robert’s mechanism
(d) Peaucellier’s mechanism

Q2. In a mechanism having 8 links, the number of instantaneous centres of rotation present are
(a) 28
(b) 56
(c) 15
(d) 0

Q3. The length of a flat plate is 2 m and width 50 cm is placed in a fluid stream at 50^o C blowing parallel to it. The convective heat transfer co-efficient of the fluid is 10 W/〖(m〗^2 K). The heat transfer takes place, if the plate is maintained at a temperature of 350^o C is
(a) 3 kW
(b) 4 kW
(c) 0.3 kW
(d) 30 kW

Q4. Resilience means
(a) Failure of material at loads less than at normal conditions
(b) Resilience of the material to elastic deformation
(c) Ability of the material to return to the original shape when load is removed.
(d) Capacity of a material to absorb energy elastically

Q5. Maximum shear stress theory was postulated by ___.
(a) St. Venant
(b) Mohr
(c) Rankine
(d) Tresca

Q6. Which of the following is TRUE for factor of safety?
(a) Tensile stress/permissible stress
(b) Compressive stress/Ultimate stress
(c) Ultimate stress/Permissible stress
(d) Ultimate stress/Shear stress

Solutions

S1. Ans. (d)
Sol. Peaucellier’s mechanism is an exact straight-line mechanism using lower pairs

S2. Ans. (a)
Sol. Center of rotation =C_2^8=(8×7)/2=28

S3. Ans(a)
Sol. by Newton’s law of cooling for convection heat transfer
Q=h A ∆T
Q=10×2×0.50×(350-50)
Q=3 kW

S4. Ans(d)
Sol.
Resilience – Capacity of a material to absorb energy elastically
Fatigue – Failure of material at loads less than at normal conditions
Stiffness – Resilience of the material to elastic deformation
Elasticity – Ability of the material to return to the original shape when load is removed.

S5. Ans.(d)
Sol. maximum shear stress theory also known as Guest & Tresca theory because it is postulated by Tresca.

S6. Ans.(c)
Sol. factor of safety is defined as the ratio of failure stress (i.e. ultimate stress) to the working stress (i.e. permissible stress)
FOS=(Ultimate stress)/(Permissible stress)

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