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UPPSC Lec’21 ME: Daily Practices Quiz. 30-Sep-2021

Quiz: Mechanical Engineering
Exam: UPPSC Lecturer
Topic: Miscellaneous

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

Q1. If the radius is doubled and the speed is reduced to half of its original value, the centrifugal force would be:
(a) 2.0 times the original value
(b) 0.5 times the original value
(c) 0.2 times the original value
(d) 0.1 times the original value

Q2. As compared to the mass of a body on the earth, its mass on the moon will be
(a) 6 times higher
(b) 6 times lower
(c) √6 times higher
(d) None of these

Q3. A solid circular shaft is subjected to pure torsion. The ratio of maximum shear stress to maximum normal stress at any point would be
(a) 1 : 1
(b) 1 : 2
(c) 2 : 1
(d) 2 : 3

Q4. Two material of shafts A and B are same, and A is thrice the diameter of B. The torque that can be transmitted by A is
(a) 3 times that of B
(b) 27 times that of B
(c) 9 times that of B
(d) 81 times that of B

Q5. In case of biaxial state of stress, normal stresses are σ_x=400 N/mm². σ_y=100 N/mm² and shear stress τ = 200 N/mm². The maximum principal stress is
(a) 800 N/mm²
(b) 900 N/mm²
(c) 500 N/mm²
(d) 1200 N/mm²

Q6. Surface defects are
(a) Grain boundaries
(b) Tilt boundary
(c) Twin boundary
(d) All of these


S1. Ans. (b)
F_2/F_1 =m_2/m_1 ×(ω_2/ω_1 )^2×r_2/r_1
=(1/2)^2×2=2/4=0.5 (∵ m_1=m_2)

S2. Ans. (d)
Sol. On moon only acceleration due to gravity is one sixth of acceleration due to gravity on earth.
So, weight of the body on moon becomes one sixth of the weight of the body on earth.
But there is no change in mass.

S3. Ans.(a)
T_e=√(M^2+ T^2 )
For pure torsion M = 0
and M_e=1/2 [ M+√(M^2+T^2 )]
∴τ_max/σ_max =1∶1

S4. Ans.(b)
Material of both shafts is same i.e., τ_perm is same
∴T ∝d^3
T_A/T_B =(d_A^3)/(d_B^3 )=3^3/1^3 =27

S5. Ans.(c)
σ_x=400 MPa;
σ_y=100 MPa
and,τ_xy=200 MPa
σ_1=1/2 [(σ_x+σ_y )+√((σ_x-σ_y )^2+4τ_xy^2 )]
=1/2 [500+√(300^2+4×200^2 )]
=500 MPa = 500 N/mm²

S6. Ans. (d)
Point Defects
Interstitial atoms
Line Defects
Edge dislocation
Screw dislocation
Surface or Grain boundaries defects
Grain boundaries
Tilt boundary
Twin boundary
Twist boundary
Volume defects
Stacking faults

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Published by VINAYAK KUMAR

Graduated from BIT Sindri, Postgraduated from IIT BHU Varanasi

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