Mechanical Design Objective Questions and Answers - Set 20 - ObjectiveBooks

# Practice Test: Question Set - 20

1. A compound cylinder with inner radius 50 mm and outer radius 70 mm is made by shrinking one cylinder on to the other cylinder, the junction radius is 60 mm and the junction pressure is 1.1 N/mm². The maximum hoop stress developed in the inner cylinder is
(A) 3.6 N/mm² compression
(B) 3.6 N/mm² tension
(C) 7.2 N/mm² compression
(D) 7.2 N/mm² tension

2. When the screw in a mechanical screw jack rotates, the load kept on the top of it moves
(A) Axially upwards
(B) Axially downwards
(C) Axially upwards or downwards
(D) None of these

3. A bolt of M 24 × 2 means that
(A) The pitch of the thread is 24 mm and depth is 2 mm
(B) Cross-sectional area of the threads is 24 mm²
(C) The nominal diameter of bolt is 24 mm and pitch is 2 mm
(D) The effective diameter of bolt is 24 mm and there are 2 threads per cm

4. Oldham coupling is used to connect two shafts
(A) Which are perfectly aligned
(B) Which are not in exact alignment
(C) Which have lateral misalignment
(D) Whose axes intersect at a small angle

5. The size of a cam depends upon
(A) Base circle
(B) Pitch circle
(C) Prime circle
(D) Pitch curve

6. According to I.B.R., the factor of safety of riveted joint should not be less than
(A) 1
(B) 2
(C) 3
(D) 4

7. When a material is subjected to fatigue loading, the ratio of the endurance limit to the ultimate tensile strength is
(A) 0.20
(B) 0.35
(C) 0.50
(D) 0.65

8. A hollow saddle key is
(A) A taper key which fits half in the key way of hub and half in the key way of shaft
(B) A taper key which fits in a key way of the hub and is flat on the shaft
(C) A taper key which fits in a key way of the hub and the bottom of the key is shaped to fit the curved surface of the shaft
(D) Provided in pairs at right angles and each key is to withstand torsion in one direction only

9. A tapered key which fits in a key way in the hub and the bottom of which is shaped to fit the curved surface of the shaft, is known as,
(B) Hollow key
(C) Soft key
(D) None of these

10. When the length of the journal is equal to the diameter of the journal, then the bearing is said to be a
(A) Short bearing
(B) Long bearing
(C) Medium bearing
(D) Square bearing

11. In order to determine the stresses in a thin cylinder due to an internal pressure, it is assumed that
(A) The effect of curvature of the cylinder wall is neglected
(B) The tensile stresses are uniformly distributed over the section of the walls
(C) The effect of the restraining action of the heads at the end of the pressure vessel is neglected
(D) All of the above

12. Two closely coiled helical springs with stiffness k₁ and k₂ respectively are connected in series. The stiffness of an equivalent spring is given by
(A) (k₁ k₂)/ (k₁ + k₂)
(B) (k₁ - k₂)/ (k₁ + k₂)
(C) (k₁ + k₂)/ (k₁ k₂)
(D) (k₁ - k₂)/ (k₁ k₂)

13. The cross-section of the arm of a bell crank lever is
(A) Rectangular
(B) Elliptical
(C) I-section
(D) Any one of these

14. Two shafts ‘A’ and ‘B’ under pure torsion are of identical length and identical weight and are made of the same material. The shaft ‘A’ is solid and the shaft ‘B’ is hollow. We can say that
(A) Shaft B is better than shaft A
(B) Shaft A is better than shaft B
(C) Both the shafts are equally good
(D) None of these

15. The connecting rod bolts are tightened up with initial tension greater than the external load so that
(A) Joint may not open up
(B) Bolts are weakest elements
(C) The resultant load on the bolt would not be affected by the external cyclic load
(D) Bolts will not loosen during service

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