NHPC JE'21 ME: Daily Practices Quiz. 01-Oct-2021

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NHPC-JE’21 ME: Daily Practices Quiz

NHPC-JE’21 ME: Daily Practices Quiz 01-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 composition of German silver is
(a) 12.5% silver
(b) 5% silver
(c) 1% silver
(d) None of the above

Q2. The velocity along the shear plane is known as
(a) Shear velocity
(b) Chip velocity
(c) Cutting velocity
(d) Mean velocity

Q3. If the ratio of the pitch of rivets to the diameter of the rivet hole is 4, then the tearing efficiency of the joint is
(a) 300 %
(b) 75 %
(c) 50 %
(d) 400 %

Q4. 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

Q5. 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

Q6. For a machine to be overhauling, its efficiency should be
(a) 100 %
(b) Less than 67 %
(c) More than 50 %
(d) Less than 50 %

Solutions

S1. Ans. (d)
Sol. There is no contamination of silver in German silver we can call it German silver just because it is appearing as silver.
German silver contains 60% cu, 20% Ni, and 20% Zn.

S2. Ans. (a)
Sol. The velocity along the tool face = chip velocity
The velocity along the shear plane = shear velocity
The velocity in the direction of cutting = cutting velocity.

S3. Ans(b)
Sol. we know that the efficiency of the riveted joint is
η=(strength of riveted joint )/(strength of plate without rivet)×100
η=((p-d)tσ_t)/(ptσ_t )×100
η=((p-d))/p×100
η=(1-d/p)×100
η=75 %
S4. 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

S5. 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.

S6. Ans(d)
Sol. If the efficiency is more than 50%, then the screw is said to be overhauling. Efficiency of self-locking screws is less than 50%.