SECTION-6

#### Theory of Machine objective type questions/Multiple choice questions

##### Q31. The maximum efficiency of a screw jack is a function of

(a) helix angle
(b) angle of friction
(d) effort.

Ans: (b) angle of friction

##### Q32. The angular velocities of the two pulleys, connected either by an open belt or a crossed belt, are

(a) directly proportional to their diameters
(b) inversely proportional to their diameters
(c) proportional to the square of their diameters
(d) proportional to the square root of their diameters.

Ans:  (b) inversely proportional to their diameters

##### Q33. Choose the wrong statement

(a) With an open belt the pulleys rotate in the same direction.
(b) The angle of contact in crossed belt drive is more than that in an open belt drive.
(c) With a crossed belt the pulleys rotate in opposite direction.
(d) The length of crossed belt depends on the sum and difference of the radii of the pulleys.

Ans:  (d) The length of crossed belt depends on the sum and difference of the radii of the pulleys.

##### Q34. When two pulleys, of unequal sizes, the connected by a belt drive the angle θ is taken as

(a) angle of contact on the bigger pulley
(b) angle of contact on the smaller pulley
(c) average angle of the contact on the two pulleys
(d) none of the above.

Ans:  (b) angle of contact on the smaller pulley

##### Q35. When the axial load carried by the shaft in case of flat collar bearing, is large; a number of collars are provided on the shaft. This is done

(a) to reduce the frictional torque
(b) to increase the frictional torque
(c) to reduce the intensity of pressure
(d) to increase the intensity of pressure.

Ans:  (c) to reduce the intensity of pressure

##### Q36. The value of limiting bearing pressure on a collar is about

(a) 1 kgf/cm2
(b) 5 kgf/cm2
(c) 10 kgf/cm2
(d) 15 kgf/cm2

Ans:  (b) 5 kgf/cm2

##### Q37. Choose the correct statement regarding the safe design of a bearing

(a) when horse power lost in friction is to be determined, uniform rate of wear is assumed
(b) when horse power transmitted is to be determined, uniform pressure is assumed
(c) when horse power lost in friction is to be determined, uniform pressure is assumed and when horse power transmitted is to be determined, uniform wear is assumed
(d) none of the above.

Ans:  (c) when horse power lost in friction is to be determined, uniform pressure is assumed and when

##### Q38. A flat foot step bearing 20 cm in diameter supports a load of 2500 kgf. The shaft is running at 420 r.p.m. and the co-efficient of friction is 0.09. The frictional torque, for uniform pressure, will be equal to

(a) 11.25 kgf-m
(b) 15 kgf-m
(c) 18.50 kgf-m
(d) 20.0 kgf-m.

Ans:  (b) 15 kgf-m

(a) l/3
(b) 2/3
(c) 1.0
(d) 4/3.

Ans:  (d) 4/3.

##### Q40. A machine is said to be self-locking if efficiency of the machine is

(a) more than 50%
(b) equal to 50%
(c) less than 50%
(d) equal to 100%.

Ans:  (c) less than 50%

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##### Read More Sections of Theory of Machine Objective Questions

Each section contains maximum 80 Questions. To practice more questions visit other sections.

Theory of Machine MCQ – Section-1

Theory of Machine MCQ – Section-2

Theory of Machine MCQ – Section-3

Theory of Machine MCQ – Section-4

Theory of Machine MCQ – Section-5

Theory of Machine MCQ – Section-6