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Engineering :: Machine Design

281.  Helical springs are not subjected to
A. Torsional shear stress B. Transverse shear stress
C. Deflection D. Hoop stress
E. Force    
282.  Friction losses in spur gears may be of the order of
A. Less than 5% B. 5% to 10%
C. 10% to 15% D. 15% to 20%
E. 20% to 30%    
283.  Which pair of gears usually has high friction losses?
A. Spur gears B. Bevel gears
C. Helical gears D. Worm and worm wheel
E. All have equal frictional loss    
284.  A pair of straight tooth bevel gears connects a pair of shafts at 90?. The velocity ratio is 3:1. The cone ptich angle of the pinion will be
A. 18.4? B. 22.5?
C. 30? D. 71.6?
E. 60?    
285.  A triple threaded worm has a pitch diameter of 100 mm and an axial pitch of 22 mm. The lead angle will be
A. tan-1 0.21 B. tan-1 0.22
C. tan-1 0.3 D. tan-1 0.36
E. tan-1 0.66    
286.  The coefficient of friction in a rolling bearing is of the order of
A. 0.1 B. 0.2
C. 0.01 D. 0.05
E. 0.001    
287.  Which of the following bearing will have least coefficient of friction?
A. Self-aligning bearing B. Cylindrical foller bearing
C. Thrust ball bearing D. Single ball bearing
E. Tapered bearing    
288.  In case of steels, as the percentage of carbon content increases
A. Tensile strength decreases B. Percentage elongation decreases
C. Hardness decreases D. Weldability increases
289.  Which material is expected to be the hardest?
A. Aluminium B. Copper-zinc
C. Molybdenum D. Brass
E. Silver    
290.  If the Brinell hardness number of a sample of steel is 200, the ultimate tensile strength will be approximately
A. 200 kgf/mm2 B. 100 kgf/mm2
C. 70 kgf/mm2 D. Cannot be determined

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