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

Quiz: Mechanical Engineering
Exam: NHPC JE
Topic: Miscellaneous

Each question carries 1 mark
Negative marking: 1/4 mark
Time: 8 Minutes

Q1. Maximum shear stress theory was postulated by ___.
(a) St. Venant
(b) Mohr
(c) Rankine
(d) Tresca

Q2. 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

Q3. A body is subjected to principal stresses at a point having value as 200 MPa, 150 MPa and 100 MPa respectively. what is the value of maximum shear stress in (MPa)
(a) 25
(b) 50
(c) 75
(d) 100

Q4. A cotter joint is used to connect two rods which are subjected to
(a) Compressive stress only
(b) Tensile as well as Compressive stress only
(c) Tensile only
(d) Shear only

Q5. The key which is used to transmits power in a taper shaft?
(a) Barth key
(b) Woodruff key
(c) Kennedy key
(d) Tangent key

Q6. Taper on the cotter and slot is provided
(a) On both the sides
(b) On one side only
(c) On none of the sides
(d) None of the above

### Solutions

S1. Ans.(d)
Sol. maximum shear stress theory also known as Guest & Tresca theory because it is postulated by Tresca.

S2. 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)

S3. Ans.(b)
Sol. Given
σ_1=200 MPa,σ_2=150 MPa,σ_3=100 MPa
Maximum shear stress
((σ_1- σ_2)/2) or =((σ_2- σ_3)/2) or ((σ_3- σ_1)/2)
So, ((200-100)/2)=50 MPa
S4. Ans. (b)
Sol. A cotter joint is used to connect to Co-axial rods, which are subjected to either axial tensile force or axial compressive force.
Cotter Joint are used in the following cases
(i) Foundation bolt
(ii) Joint between the piston rod and the tail or pump rod.
(iii) Joint between the slide spindle and the fork of the valve mechanism
(iv) Joint between the piston and the cross head of a steam Engine

S5. Ans. (b)
Sol. The woodruff key is used to transmits power in a taper shaft.

S6. Ans. (b)
Sol. Taper on the cotter and slot is provided on one side only.

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