Quiz: Mechanical Engineering
Exam: NHPC JE
Each question carries 1 mark
Negative marking: 1/4 mark
Time: 8 Minutes
Q1. Maximum shear stress theory was postulated by ___.
(a) St. Venant
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)
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
Sol. maximum shear stress theory also known as Guest & Tresca theory because it is postulated by Tresca.
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)
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.