POWER SCREW
25 January 2022 19:33
UNIT-POWER SCREW
1. Which of the following screw thread is used for jacks, vices and clamps?
(a) square threads (b) trapezoidal threads
(c) buttress threads (d) acme threads
2. Which of the following screw thread is used for transmitting power in either direction?
(a) square threads (b) trapezoidal threads
(c) Buttress threads (d) (a) and (b)
3. Which of the following screw thread is used for transmitting force in one direction?
(a) square threads (b) trapezoidal threads
(c) Buttress threads (d) V threads LOKHANDE SIR'S TUTORIAL
4. Which of the following screw thread is stronger than other threads?
(a) square threads (b) trapezoidal threads
(c) Buttress threads (d) V threads
5. Which of the following screw thread is used for lead screw of lathe?
(a) square threads (b) trapezoidal threads
(c) Buttress threads (d) V threads
6. Multiple threads are used to secure
(a) high efficiency (b) high mechanical advantage
(c) low efficiency for self-locking (d) high load carrying capacity
7. Power screws for transmission of power should have
(a) high efficiency (b) low efficiency
(c) self-locking characteristic (d) over hauling characteristic
8. The efficiency of square threaded power screw is given by,
LOKHANDE SIR'S TUTORIAL
where a = helix angle f = friction angle
10. For self locking screw
(a) f > a
MD MCQS Page 1
10. For self locking screw
(a) f > a
(b)m < tan a
(c) a > f
(d)m = cosec a
where a = helix angle f = friction angle
11. For over hauling screw
m = coefficient of friction
(a) f > a
(c) f = a
(b) a > f
(d) none of above LOKHANDE SIR'S TUTORIAL
where a = helix angle f = friction angle m = coefficient of friction
12. A screw is said to be self-locking if its efficiency is
(a) equal to 50% (b) more than 50%
(c) less than 50% (d) none of the above
13. A screw is said to be over hauling if its efficiency is
(a) equal to 50% (b) more than 50%
(c) less than 50% (d) none of the above
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14. In design of screw jack from buckling considerations, the end conditions are assumed as
(a) both ends are hinged (b) both ends are fixed
(c) one end fixed and other hinged (d) one end fixed and other free
15. A cup is provided in screw jack
(a) to reduce the friction (b) to prevent rotation of load
(c) to increase load capacity (d) To increase efficiency
16. The efficiency of square threaded power is maximum when
where a = helix angle f = friction angle
17. The maximum efficiency of square threaded power is
where f = friction angle
a) (1 - sin f)/(1 + sin f)
b) (1 - tan f)/ ( 1 + tan f)
c) (1 + sin f)/(1 - sin f) LOKHANDE SIR'S TUTORIAL
d) (1 + tan f)/(1 - tan f)
18. The maximum efficiency of square threaded power depends upon
(a) lead angle of screw (b) friction angle
(c) pitch of screw (d) nominal diameter of screw
19. The efficiency of square threaded power depends upon
(a) mean diameter of screw (b) coefficient of friction
(c) pitch of screw (d) All the above
20. The maximum efficiency of square threaded power with friction angle of 30 0 is
(a) 25% (b) 33%
(c) 47% (d) 41%
MD MCQS Page 2
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21. By using large thread angle in lifting machines
(a) the mechanical advantage is more
(b) the mechanical advantage is less
(c) the load will be sustained in absence of any effort
(d) the load is easily lifted
22. A power screw is specified by
(a) major diameter x pitch (b) major diameter x length
(c) mean diameter x pitch (d) nominal major diameter
33. Trapezoidal threads are better than square threads as there is radial pressure or side
thrust on the nut.
a) True
b) False. LOKHANDE SIR'S TUTORIAL
34. Which of the following are true for buttress threads?
a) Combination of square and trapezoidal threads
b) Transmit motion in one direction only
c) They are used in vices
d) All of the mentioned.
35. Tr 40 x 14(P 7), here 14 indicates
a) Pitch
b) Lead
c) Diameter
d) None of the mentioned
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36. If nominal diameter of screw thread=50mm and pitch=10mm then the mean diameter of
the screw thread will be?
a) 40mm
b) 45mm.
c) 60mm
d) 55mm
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MD MCQS Page 3
