371. The radius of a friction circle for a shaft rotating inside a bearing is (where r = Radius of shaft, and tan φ = Coefficient of friction between the shaft and bearing)
r sin φ
r cos φ
r tan φ
✅ The correct answer is option A.
Theory of machines MCQs
372. In a flat collar pivot bearing, the moment due to friction is proportional to
✅ The correct answer is option C.
373. The frictional torque transmitted in a flat collar bearing, considering uniform pressure, is (where r1 and r2 = External and internal radii of collar respectively)
μ W (r1 + r2)
μ W (r1 + r2)
✅ The correct answer is option D.
374. A shaft has two heavy rotors mounted on it. The transverse natural frequencies, considering each of the rotor separately, are 100 Hz and 200 Hz respectively. The lowest critical speed is
5367 r.p.m.
6000 r.p.m.
9360 r.p.m.
12000 r.p.m.
✅ The correct answer is option A.
376. The velocity of the rubbing surface __________ with the distance from the axis of the bearing.
increases
decreases
✅ The correct answer is option A.
377. The two parallel and coplaner shafts are connected by gears having teeth parallel to the axis of the shaft. This arrangement is known as
spur gearing
helical gearing
bevel gearing
spiral gearing
✅ The correct answer is option A.
378. In a differential band brake as shown in the below figure, the drum rotates anticlockwise and the greater tension T1 acts at A and smaller tension T2 at B. Length OA is greater than length OB. In order to apply the brake, the force P at C should
be zero
act in upward direction
act in downward direction
none of the above
✅ The correct answer is option C.
379. In the below figure, PC is the connecting rod and OC is the crank making an angle θ with the line of stroke PO and rotates with uniform angular velocity at ω rad/s. The Klien’s acceleration diagram for determining the acceleration of the piston P is shown by quadrilateral C Q NO, if N coincides with O, then
acceleration and velocity of the piston P is zero
acceleration and velocity of the piston P is maximum
acceleration of the piston P is zero and its velocity is maximum
acceleration of the pi
✅ The correct answer is option C.
380. When the nature of contact between the elements of a pair is such that it can only slide relative to the other, the pair is known as a
screw pair
spherical pair
turning pair
sliding pair
✅ The correct answer is option D.