1. For full depth of involute spur gears, minimum number of teeth of pinion to avoid interference depends upon
(a) Pressure angle
(b) Speed ratio
(c) Circular pitch
(d) Pitch diameter
(1 Mark, 1988)

Ans: b
2. Morden gear tooth profile is given involute shape because
(a) This is a very easy curve for manufacturing.
(b) Sliding does not takes place anywhere on meshing teeth.
(c) Involute is the only profile that gives conjugate action.
(d) Change in the centre distance does not change gear ratio.
(1 Mark, 1989)

Ans: d
3. In order to test the efficiency of reducer gear train 1 kW input was given at the input end at a speed of 1440 rpm and the output end the measure torque was 56.36 Nm. If the ratio of speed reduction in this unit is 10:1, the efficiency is about
(a) 78%
(b) 85%
(c) 63%
(d) 96%
(2 Mark, 1989)

Ans: b
4. For a pinion of 15 teeth, under cutting _____ (increases/ decreases) with ____ (increase/ decrease) of pressure angle.
(1 Mark, 1991)

Ans: decreases, increase
5. The sun gear in the figure is driven clockwise at 100 rpm. The ring gear is held stationary. For the number of teeth shown on the gears, the arm rotates at
(b) 20 rpm
(c) 33.33 rpm
(d) 66.67 rpm
(2 Mark, 1993)

Ans: b
6. In spur gears having involute teeth, the product of circular pitch and diametric pitch is __.
(1 Mark, 1994)

Ans: \pi
7. Match correct pairs between List I and List II.
(a) A – 2, B – 3, C – 1, D – 4
(b) A – 4, B – 1, C – 3, D – 2
(c) A – 4, B – 3, C – 2, D – 1
(d) A – 3, B – 1, C – 2, D – 4
(2 Mark, 1995)

Ans: c
8. The arm OA of an epicyclic gear train shown in figure revolves counter clockwise about O with an angular velocity of 4 rad/sec. Both gears are of same size. The angular velocity of gear C, if the sun gear B is fixed, is:
(a) 4 rad/sec
(b) 8 rad/sec
(c) 10 rad/sec
(d) 12 rad/sec
(2 Mark, 1995)

Ans: b
9. Interference in a pair of gears is avoided, if the addendum circles of both the gears intersect common tangent to the base circles within the points of tangency. (True/ False)
(1 Mark, 1995)

Ans: True
10. In spur gears, the circle on which the involute is generated is called the
(a) Pitch circle
(b) Clearance circle
(c) Base circle
(d) Addendum circle
(1 Mark, 1996)

Ans: c
11. To make a worm drive reversible, it is necessary to increase
(a) Centre distance
(b) Worm diameter factor
(c) Number of starts
(d) Reduction ratio
(1 Mark, 1997)

Ans: c
12. A 1.5 kW motor is running at 1440 rev/min. It is to be connected to a stirrer running at 36 rev/min. The gearing arrangement suitable for this application is
(a) differential gear
(b) helical gear
(c) spur gear
(d) worm gear
(1 Mark, 2000)

Ans: d
13. Large speed reductions (greater than 20) in one stage of a gear train are possible through
(a) Spur gearing
(b) Worm gearing
(c) Bevel gearing
(d) Helical gearing
(1 Mark, 2002)

Ans: b
14. The minimum number of teeth on the pinion to operate without interference in standard full height involute teeth gear mechanism with 20° pressure angle is
(a) 14
(b) 12
(c) 18
(d) 32
(1 Mark, 2002)

Ans: c
Common data questions (15, 16).
The overall gear ratio in a 2 stage speed reduction gear box (with all spur gears) is 12. The input and output shafts of the gear box are collinear. The countershaft which is parallel to the input and output shafts has a gear (Z_{2} teeth) and pinion (Z_{3} = 15 teeth) to mesh with pinion (Z_{1} = 16 teeth) on the input shaft and gear (Z_{4} teeth) on the output shaft respectively. It was decided to use a gear ratio of 4 with 3 module in the first stage and 4 module in the second stage.
15. Z_{2} and Z_{4} are
(a) 64 and 45
(b) 45 and 64
(c) 48 and 60
(d) 60 and 48
(1 Mark, 2003)

Ans: a
16. The center distance in the second stage is
(a) 90 mm
(b) 120 mm
(c) 160 mm
(d) 240 mm
(1 Mark, 2003)

Ans: b
17. Two mating spur gears have 40 and 120 teeth respectively. The pinion rotates at 1200 rpm and transmits a torque of 20 N.m. The torque transmitted by the gear is
(a) 6.6 Nm
(b) 20 Nm
(c) 40 Nm
(d) 60 Nm
(1 Mark, 2004)

Ans: d
18. Match the following.
(a) P – 4, Q – 2, R – 1, S – 3
(b) P – 2, Q – 3, R – 4, S – 1
(c) P – 3, Q – 2, R – 1, S – 4
(d) P – 1, Q – 3, R – 4, S – 2
(2 Mark, 2004)

Ans: b
Data for Q.19 – 20 are given below.
A compacting machine shown in the figure below is used to create a desired thrust force by using a rack and pinion arrangement. The input gear is mounted on the motor shaft. The gears have involute teeth of 2 mm module.
19. If the drive efficiency is 80%, the torque required on the input shaft to create 1000 N output thrust is
(a) 20 Nm
(b) 25 Nm
(c) 32 Nm
(d) 50 Nm
(2 Mark, 2004)

Ans: b
20. If the pressure angle of the rack is 20^{0}, the force acting along the line of action between the rack and the gear teeth is
(a) 250 N
(b) 342 N
(c) 532 N
(d) 600 N
(2 Mark, 2004)

Ans: c
Common Data for Questions 21, 22:
A planetary gear train has four gears and one carrier. Angular velocities of the gears are ω_{1}, ω_{2}, ω_{3} and ω_{4} respectively. The carrier rotates with angular velocity ω_{5}.
21. What is the relation between the angular velocities of gear 1 and gear 4?
(a) \frac { { \omega }_{ 1 }{ \omega }_{ 5 } }{ { \omega }_{ 4 }{ \omega }_{ 5 } } =6
(b) \frac { { \omega }_{ 4 }{ \omega }_{ 5 } }{ { \omega }_{ 1 }{ \omega }_{ 5 } } =6
(c) \frac { { \omega }_{ 4 }{ \omega }_{ 5 } }{ { \omega }_{ 1 }{ \omega }_{ 5 } } =\left( \frac { 2 }{ 3 } \right)
(d) \frac { { \omega }_{ 2 }{ \omega }_{ 5 } }{ { \omega }_{ 4 }{ \omega }_{ 5 } } =6
(2 Mark, 2006)

Ans: a
22. For ω_{1} = 60 rpm clockwise (cw) when looked from the left, what is the angular velocity of the carrier and its direction so that Gear 4 rotates in counterclockwise (ccw) direction at twice the angular velocity of Gear 1 when looked from the left
(a) 130 rpm, cw
(b) 223 prm, ccw
(c) 256 rpm, cw
(d) 156 rpm, ccw
(2 Mark, 2006)

Ans: d
23. Twenty degree full depth involute profiled 19tooth pinion and 37tooth gear are in mesh. If the module is 5 mm, the center distance between the gear pair will be
(a) 140 mm
(b) 150 mm
(c) 280 mm
(d) 300 mm
(2 Mark, 2006)

Ans: a
Linked Questions. (24, 25, 26)
A gear set has a pinion with 20 teeth and a gear with 40 teeth. The pinion runs at 30 rev/s and transmits a power of 20 kW. The teeth are on the 20^{0} fulldepth system and have a module of 5 mm. The length of the line of action is 19 mm.
24. The center distance for the above gear set in mm is
(a) 140
(b) 150
(c) 160
(d) 170
(2 Mark, 2007)

Ans: b
25. The contact ratio of the contacting tooth is
(a) 1.21
(b) 1.25
(c) 1.29
(d) 1.33
(2 Mark, 2007)

Ans: c
26. The resultant force on the contacting gear tooth in N is
(a) 77.23
(b) 212.20
(c) 2258.1
(d) 289.43
(2 Mark, 2007)

Ans: c
27. Match the following.
Types of gears 

(P) Helical 
(1) Axes non parallel and nonintersection 
(Q) Spiral Bevel 
(2) Axes parallel and teeth are inclined to the axis 
(R) Hypoid 
(3) Axes are parallel and teeth are parallel to the axis 
(S) Rack and pinion 
(4) Axes are perpendicular and intersecting, and teeth are inclined to the axis 

(5) Axes are perpendicular and used for large speed reduction 

(6) Axes parallel and one of the gears has infinite radius 
(a) P – 2, Q – 4, R – 1, S – 6
(b) P – 1, Q – 4, R – 5, S – 6
(c) P – 2, Q – 6, R – 4, S – 2
(d) P – 6, Q – 3, R – 1, S – 5
(2 Mark, 2008)

Ans: a
28. An epicyclic gear train is shown schematically in the adjacent figure. The sun gear 2 on the input shaft is a 20 teeth external gear. The planet gear 3 is a 40 teeth external gear. The ring gear 5 is a 100 teeth internal gear. The ring gear 5 is fixed and the gear 2 is rotating at 60 rpm ccw (ccw=counterclockwise and cw=clockwise). The arm 4 attached to the output shaft will rotate at
(a) 10 rpm ccw
(b) 10 rpm cw
(c) 12 rpm cw
(d) 12 rpm ccw
(2 Mark, 2009)

Ans: a
29. Tooth interference in an external involute spur gear pair can be reduced by
(a) decreasing center distance between gear pair
(b) decreasing module
(c) decreasing pressure angle
(d) increasing number of gear teeth
(2 Mark, 2009)

Ans: d
30. For the epicyclic gear arrangement shown in the figure, ω_{2} = 100 rad/s clockwise (CW) and ω_{arm} = 80 rad/s counter clockwise (CCW). The angular velocity ω_{5} (in rad/s) is
(a) 0
(b) 70CW
(c) 140CCW
(d) 140CW
(2 Mark, 2010)

Ans: c
31. The following are the data for two crossed helical gears used for speed reduction:
Gear I: Pitch circle diameter in the plane of rotation 80 mm and helix angle 30º.
Gear II: Pitch circle diameter in the plane of rotation 120 mm and helix angle 22.5º.
If the input speed is 1440 rpm, the output speed in rpm is
(a) 1200
(b) 900
(c) 875
(d) 720
(1 Mark, 2012)

Ans: b
32. A compound gear train with gears P, Q, R and S has number of teeth 20, 40, 15 and 20, respectively. Gears Q and R are mounted on the same shaft as shown in the figure below. The diameter of the gear Q is twice that of the gear R. If the module of the gear R is 2 mm, the center distance in mm between gears P and S is
(a) 40
(b) 80
(c) 120
(d) 160
(2 Mark, 2013)

Ans: b
33. A pair of spur gears with module 5 mm and a center distance of 450 mm is used for a speed reduction of 5:1. The number of teeth on pinion is _______.
(1 Mark, 2014[1])

Ans: 30
34. For the given statements:
I. Mating spur gear teeth is an example of higher pair.
II. A revolute joint is an example of lower pair.
Indicates the correct answer.
(a) Both I and II are false.
(b) I is true and II is false.
(c) I is false and II is true.
(d) Both I and II are true.
(1 Mark, 2014[1])

Ans: d
35. Gear 2 rotates at 1200 rpm in counter clockwise direction and engages with Gear 3 and Gear 4 are mounted on the same shaft. Gear 5 engages with Gear 4. The numbers of teeth on Gears 2, 3, 4 and 5 are 20, 40, 15 and 30, respectively. The angular speed of Gear 5 is
(a) 300 rpm counterclockwise
(b) 300 rpm clockwise
(c) 4800 rpm counterclockwise
(d) 4800 rpm clockwise
(1 Mark, 2014[3])

Ans: a
36. It is desired to avoid interference in a pair of spur gears having a 20° pressure angle. With increase in pinion to gear speed ratio, the minimum number of teeth on the pinion
(a) increases
(b) decreases
(c) first increases and then decreases
(d) remains unchanged
(2 Mark, 2014[4])

Ans: a
37. Which one of the following is used to convert a rotational motion into a translational motion?
(a) Bevel gears
(b) Double helical gears
(c) Worm gears
(d) Rack and pinion gears
(1 Mark, 2014[4])

Ans: d
38. The number of degrees of freedom of the planetary gear train shown in the figure is
(a) 0
(b) 1
(c) 2
(d) 3
(1 Mark, 2015[2])

Ans: 2
Explanation:
F = 3(N – 1) – 2j – h
F = 3(4 – 1) – 2(3) – 1
F = 2
39. A gear train is made up of five spur gears as shown in the figure. Gear 2 is driver and gear 6 is driven member. N_{2}, N_{3}, N_{4}, N_{5} and N_{6} represent number of teeth on gears 2, 3, 4, 5 and 6 respectively. The gear(s) which act(s) as idler(s) is/are
(a) Only 3
(b) Only 4
(c) Only 5
(d) Both 3 and 5
(1 Mark, 2015[3])

Ans: c
Explanation:
A gear which does not affect the speed ratio between the input and the output shaft is called an idler gear.
Here, gear 5 is a idler gear.
40. In the gear train shown, gear 3 is carried on arm 5. Gear 3 meshes with gear 2 and gear 4. The number of teeth on gear 2, 3, and 4 are 60, 20, and 100, respectively. If gear 2 is fixed and gear 4 rotates with an angular velocity of 100 rpm in the counterclockwise direction, the angular speed of arm 5 (in rpm) is
(a) 166.7 counterclockwise
(b) 166.7 clockwise
(c) 62.5 counterclockwise
(d) 62.5 clockwise
(2 Mark, 2016[1])

Ans: c
41. In an epicyclic gear train, shown in the figure, the outer ring gear is fixed, while the sun gear rotates counterclockwise at 100 rpm. Let the number of teeth on the sun, planet and outer gears to be 50, 25 and 100, respectively. The ratio of magnitude of angular velocity of the planet gear to the angular velocity of the carrier arm is ______.
(2 Mark, 2017[1])

Ans: 3
42. A gear train shown in the figure consists of gears P, Q, R and S. Gear Q and gear R are mounted on the same shaft. All the gears are mounted on parallel shafts and the number of teeth of P, Q, R and S are 24, 45, 30 and 80, respectively. Gear P is rotating at 400 rpm. The speed (in rpm) of the gear S is _______.
(2 Mark, 2017[2])

Ans: 120
43. An epicyclic gear train is shown in the figure below. The number of teeth on the gears A, B and D are 20, 30 and 20, respectively. Gear C has 80 teeth on the inner surface and 100 teeth on the outer surface. If the carrier arm AB is fixed and the sun gear A rotates at 300 rpm in the clockwise direction, then the rpm of D in the clockwise direction is
(a) 240
(b) 240
(c) 375
(d) 375
(2 Mark, 2018[1])

Ans: c
44. A frictionless gear train is shown in the figure. The leftmost 12teeth gear is given a torque of 100 Nm. The output torque from the 60teeth gear on the right in Nm is
(a) 5
(b) 20
(c) 500
(d) 2000
(1 Mark, 2018[2])

Ans: d
45. A spur gear has pitch circle diameter D and number of teeth T. The circular pitch of the gear is
(a) πD/T
(b) T/D
(c) D/T
(d) 2πD/T
(1 Mark, 2019[2])

Ans: a