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# Multiple choice question for engineering

## Set 1

1. If the centre distance between a pair of spur gears in mesh is 240 mm and the pinion moves five times faster than the gear, then the pitch circle diameters of pinion and gear respectively are
a) 40mm and 200 mm
b) 80mm and 400 mm
c) 60mm and 300 mm
d) 50mm and 250 mm

Answer: b [Reason:] rp + rg = 240 rp/rg = 5 rg = 200 mm, dg = 400 mm rp = 40 mm, dp = 80 mm.

2. Pressure angle of involute gears does not exceed 250, since
a) this will lead to unwanted radial force
b) the number of teeth to avoid undercutting will be very high
c) no cutters are available
d) gear will become too small

Answer: a [Reason:] Pressure angle of involute gears does not exceed 250, since Gear is curved.

3. Worm and worm wheel drive can be reversible.
a) True
b) False

Answer: a [Reason:] If friction angle > lead angle we cannot determine whether drive is reversible or not.

4. Two involute gears are designed to mesh for a given centre distance and a given angular velocity ratio (other than 1). During assembly, the centre distance has increased slightly. Then which of the following changes occur?
(i) Velocity ratio changes
(ii) Pressure angle changes
(iii) Pitch circle diameter changes
(iv) Working depth changes
(v) Base circle radius changes
Select the correct answer using the code given below.
a) 1, 2 and 3
b) 2, 3 and 4
c) 2 and 5
d) 3 and 5

Answer: b [Reason:] When Centre to centre distance increases then pressure angle, depth, pitch circle diameter changes. Velocity ratio and base circle radius will remain same.

5. Which of the following statements are correct for mating gears with involute profiles?
(i) The pressure angle, from the start of the engagement to the end of the engagement, remains constant.
(ii) The pressure angle is maximum at the beginning of the engagement, reduces to zero at pitch point, starts decreasing and again becomes maximum at the end of the engagement.
(iii) The face and flank of the teeth are generated by a single curve and the normal to this curve at any point is tangent to the base circle of the gear.
(iv) The centre distance for a pair of mating gears can be varied within limits without altering the velocity ratio.
Select the correct answer using the code given below.
a) 1, 3 and 4
b) 1 and 3 only
c) 2 and 4 only
d) 2,3 and 4

Answer: a [Reason:] The pressure angle varies only for cycloidal gears.

6. The velocity ratio in the case of the compound train of wheels is equal to
a) No. of teeth on first driver/No.of teeth on last follower
b) No. of teeth on last follower/No.of teeth on first driver
c) Product of teeth on the drivers/Product of teeth on the followers
d) Product of teeth on the followers/Product of teeth on the drivers

Answer: c [Reason:] In compound trains, velocity ratio = Product of teeth on the drivers/Product of teeth on the followers.

7. Match list I with list II
List I List II
A. Compound train 1. Hart mechanism
B. Quick return mechanism 2. Coriolis force
C. Exact straight line motion 3. Transmission of motion around bends and corners
D. Approximate straight line motion 4. Watt mechanism

a) A-1,B-2,C-3,D-4
b) A-3,B-2,C-1,D-4
c) A-3,B-4,C-1,D-2
d) A-1,B-4,C-3,D-2

Answer: b [Reason:] Compound train – Transmission of motion around bends and corners Quick return mechanism – Coriolis force Exact straight line motion – Hart mechanism Approximate straight line motion – Watt mechanism.

8. Consider the following statements:
When two gears are meshing, the clearance is given by the
1. difference between dedendum of one gear and addendum of the mating gear.
2. difference between total and the working depth of a gear tooth.
3. distance between the bottom land of one gear and the top land of the mating gear.
4. difference between the radii of the base circle and the dedendum circle.

Which of these statements are correct?
a) 1,2 and 3
b) 2,3 and 4
c) 1,3 and 4
d) 1,2 and 4

Answer: d [Reason:] the clearance can be found by following points 1,2 and 4.

9. In a simple gear train, if the number of idler gears is odd, then the direction of motion of driven gear will
a) be same as that of the driving gear
b) be opposite to that of the driving gear
c) depend upon the number of teeth on the driving gear
d) depend upon the total number of teeth on all gears of the train

Answer: a [Reason:] In case of odd number of gears in a simple gear train, then the direction of motion of driven gear will be same as that of driving gear.

10. An epicyclic gear train has 3 shafts A,B and C. A is an input shaft running at 100 r.p.m. clockwise. B is an output shaft running at 250 r.p.m. clockwise. Torque on a is 50 kNm. C is a fixed shaft. The torque to fix C
a) is 20 kNm anticlockwise
b) is 30 kNm anticlockwise
c) is 30 kNm clockwise
d) cannot be determined as the data is insufficient

Answer: a [Reason:] TA ωA = TB ωB 50 x 100 = TB x 250 or, TB = 20 kNm Torque on C will be same as on B but in inverse direction.

## Set 2

1. When the rubbing surfaces are separated from each other by a very thin film of lubricant it is known as
a) kinetic friction
b) dry friction
c) boundary lubrication
d) none of the mentioned

Answer: c [Reason:] When the rubbing surfaces are separated from each other by a very thin film of lubricant it is known as boundary lubrication. When the two solid surfaces sliding over each other are free from contaminating fluid or film, the resistance encountered is called dry friction.

2. Sliver sulphate, tungsten disulphide, graphite, molybdenum disulphide, lead oxide are examples of
a) boundary lubrication
b) viscous lubrication
c) solid lubrication
d) none of the mentioned

Answer: c [Reason:] Sliver sulphate, tungsten disulphide, graphite, molybdenum disulphide, lead oxide are examples of solid lubrication. Step bearing is used to resist the end thrust of the shafts.

3. __________ is used to resist the end thrust of the shafts.
a) friction circle
b) step bearings
c) injector
d) none of the mentioned

Answer: b [Reason:] Step bearing is used to resist the end thrust of the shafts.

4. When the two solid surfaces sliding over each other are free from contaminating fluid or film, the resistance encountered is called
a) kinetic friction
b) dry friction
c) boundary lubrication
d) none of the mentioned

Answer: b [Reason:] When the two solid surfaces sliding over each other are free from contaminating fluid or film, the resistance encountered is called dry friction. When the rubbing surfaces are separated from each other by a very thin film of lubricant it is known as boundary lubrication.

5. For design of ordinary machinery, value of journal friction can be taken as
a) 0.008 to 0.02
b) 0.07 to 0.15
c) 0.05 to 0.80
d) none of the mentioned

Answer: a [Reason:] For very low velocities of rotation, high loads, and with good lubrication can be taken as 0.07 to 0.15. For design of ordinary machinery, value of journal friction can be taken as 0.008 to 0.02.

6. For very low velocities of rotation, high loads, and with good lubrication can be taken as
a) 0.008 to 0.02
b) 0.07 to 0.15
c) 0.05 to 0.80
d) none of the mentioned

Answer: b [Reason:] For very low velocities of rotation, high loads, and with good lubrication can be taken as 0.07 to 0.15. For design of ordinary machinery, value of journal friction can be taken as 0.008 to 0.02.

7. When the lubrication is arranged so that rubbing surfaces are separated by a fluid film, and the load on the surfaces is carried entirely by the hydrostatic or hydrodynamic pressure in the film, it is known as
a) boundary lubrication
b) viscous lubrication
c) solid lubrication
d) none of the mentioned

Answer: b [Reason:] When the lubrication is arranged so that rubbing surfaces are separated by a fluid film, and the load on the surfaces is carried entirely by the hydrostatic or hydrodynamic pressure in the film, it is known as viscous lubrication. When the rubbing surfaces are separated from each other by a very thin film of lubricant it is known as boundary lubrication.

8. When the load on the rubbing surfaces is carried partly by a fluid viscous film and partly by areas of boundary lubrication, it is known as
a) incomplete lubrication
b) viscous lubrication
c) solid lubrication
d) none of the mentioned

Answer: a [Reason:] When the lubrication is arranged so that rubbing surfaces are separated by a fluid film, and the load on the surfaces is carried entirely by the hydrostatic or hydrodynamic pressure in the film, it is known as viscous lubrication. When the rubbing surfaces are separated from each other by a very thin film of lubricant it is known as boundary lubrication. When the load on the rubbing surfaces is carried partly by a fluid viscous film and partly by areas of boundary lubrication, it is known as incomplete lubrication.

9. When effect of friction is negligible, the force is transmitted by the link from driver to the driven link through the centre line of the pins connecting the link. With friction, the line of action shifts and is tangent to _____________
a) kinetic friction
b) dry friction
c) friction circle
d) none of the mentioned

Answer: c [Reason:] When effect of friction is negligible, the force is transmitted by the link from driver to the driven link through the centre line of the pins connecting the link. With friction, the line of action shifts and is tangent to friction circle. When the load on the rubbing surfaces is carried partly by a fluid viscous film and partly by areas of boundary lubrication, it is known as incomplete lubrication.

10. If one surface slides over the other, being pressed together by a normal force N, a frictional force F resisting the motion must be overcome. The ratio F/N is called ______________
a) kinetic friction
b) dry friction
c) friction circle
d) none of the mentioned

Answer: a [Reason:] If one surface slides over the other, being pressed together by a normal force N, a frictional force F resisting the motion must be overcome. The ratio F/N is called kinetic friction. When the two solid surfaces sliding over each other are free from contaminating fluid or flim, the resistance encountered is called dry friction.

## Set 3

1. The acceleration of a particle at any instant has two components, radial component and tangential component. These two components will be
a) parallel to each other
b) perpendicular to each other
c) inclined at 450
d) opposite to each other

Answer: b [Reason:] Both the components will be perpendicular to each other.

2. The centre of gravity of a coupler link in a four bar mechanism will experience
a) no acceleration
b) only linear acceleration
c) only angular acceleration
d) both linear and angular acceleration

Answer: d [Reason:] None

3. When a point moves along a straight line, its acceleration will have
a) radial component only
b) tangential component only
c) coriolis component only
d) radial and tangential components both

Answer: b [Reason:] The tangential component, is parallel to the velocity of the particle at the given instant. The centripetal or radial component, is perpendicular to the velocity of the particle at the given instant.

4. When a point at the end of a link moves with constant angular velocity, its acceleration will have
a) radial component only
b) tangential component only
c) coriolis component only
d) radial and tangential components both

Answer: a [Reason:] The centripetal or radial component, is perpendicular to the velocity of the particle at the given instant. The tangential component, is parallel to the velocity of the particle at the given instant.

5. In a shaper mechanism, the coriolis component of acceleration does not exists.
a) True
b) False

Answer: b [Reason:] In a shaper mechanism, the coriolis component of acceleration exists.

6. The tangential component of acceleration of the slider with respect to the coincident point on the link is called coriolis component of acceleration.
a) True
b) False

Answer: a [Reason:] When a point on one link is sliding along another rotating link, such as in quick return motion mechanism, then the coriolis component of the acceleration must be calculated.

7. The coriolis component of acceleration acts
a) along the sliding surface
b) perpendicular to the sliding surface
c) at 450 to the sliding surface
d) parallel to the sliding surface

8. The coriolis component of acceleration is taken into account for
a) slider crank mechanism
b) four bar chain mechanism
c) quick return motion mechanism
d) all of the mentioned

Answer: c [Reason:] When a point on one link is sliding along another rotating link, such as in quick return motion mechanism, then the coriolis component of the acceleration must be calculated.

9. The coriolis component of acceleration depends upon
a) velocity of slider
b) angular velocity of the link
c) all of the mentioned
d) none of the mentioned

10. A body in motion will be subjected to coriolis acceleration when that body is
a) in plane rotation with variable velocity
b) in plane translation with variable velocity
c) in plane motion which is a resultant of plane translation and rotation
d) restrained to rotate while sliding over another body

Answer: d [Reason:] When a point on one link is sliding along another rotating link, such as in quick return motion mechanism, then the coriolis component of the acceleration must be calculated.

11. A slider moves at a velocity v on a link revolving at ωrad/s. The coriolis component of acceleration is
a) ωv
b) 2ωv
c) ω2v
d) 2ωv2

12. The coriolis component of acceleration leads the sliding velocity by
a) 450
b) 900
c) 1350
d) 1800

Answer: b [Reason:] The direction of coriolis component of acceleration is obtained by rotating v, at 90°, about its origin in the same direction as that of ω.

13. The sense of coriolis component 2ωv is same as that of the relative velocity vector v rotated at
a) 450 in the direction of rotation of the link containing the path
b) 450 in the direction opposite to the rotation of the link containing the path
c) 900 in the direction of rotation of the link containing the path
d) 1800 in the direction opposite to the rotation of the link containing the path

Answer: c [Reason:] The direction of coriolis component of acceleration is obtained by rotating v, at 90°, about its origin in the same direction as that of ω.

## Set 4

1. The relative velocity of B with respect to A in a rigid link AB is
a) parallel to AB
b) perpendicular to AB
c) along AB
d) at 450

Answer: b [Reason:] The relative velocity of any two points on a rigid link is always normal to the line joining the two points.

2. The magnitude of linear velocity of a point B on a link AB relative to point A is
a) ω x AB
b) ω(AB)2
c) ω2AB
d) (ω x AB)2

3. The direction of linear velocity of any point on a link with respect to another point on the same link is
a) parallel to the link joining the points
b) perpendicular to the link joining the points
c) at 450 to the link joining the points
d) none of the mentioned

Answer: b [Reason:] The relative velocity of any two points on a rigid link is always normal to the line joining the two points.

4. The two links OA and OB are connected by a pin joint at O. If the link OA turns with angular velocity ω1 rad/s in the clockwise direction and the link OB turns with angular velocity ω2 rad/s in the anti-clockwise direction, then the rubbing velocity at the pin joint O is
a) ω12.r
b) (ω12)r
c) (ω12)r
d) (ω12)2r

Answer: c [Reason:] Consider two links OA and OB connected by a pin joint at O Let ω1 = Angular velocity of the link OA or the angular velocity of the point A with respect to O. ω2 = Angular velocity of the link OB or the angular velocity of the point B with respect to O, and r = Radius of the pin. According to the definition, Rubbing velocity at the pin joint O = (ω1 – ω2) r, if the links move in the same direction = (ω1 + ω2) r, if the links move in the opposite direction

5. In the above question, if both the links OA and OB turns in clockwise direction, then the rubbing velocity at the pin joint O is
a) ω12.r
b) (ω12)r
c) (ω12)r
d) (ω12)2r

Answer: b [Reason:] Consider two links OA and OB connected by a pin joint at O Let ω1 = Angular velocity of the link OA or the angular velocity of the point A with respect to O. ω2 = Angular velocity of the link OB or the angular velocity of the point B with respect to O, and r = Radius of the pin. According to the definition, Rubbing velocity at the pin joint O = (ω1 – ω2) r, if the links move in the same direction = (ω1 + ω2) r, if the links move in the opposite direction

6. ABCD is a four bar mechanism in which AB = 310mm and CD = 450mm. AB and CD are both perpendicular to the fixed link AD. If the velocity of B at this condition is v. Then the velocity of C is
a) v
v) 2/3 v
c) 3/2 v
d) 9/4 v

Answer: c [Reason:] Velocity at C = CD/AB x velocity at B = 450/310 x v = 3/2 v

7. A thin circular disc is rolling with a uniform linear speed, along a straight path on a plane surface. Which of the following statement is correct in this regard?
a) All points of the disc have the same velocity.
b) The centre of the disc has zero acceleration.
c) The centre of the disc has centrifugal acceleration.
d) The point on the disc making contact with the plane surface has zero acceleration.

8. The component of the accelertion, parallel to the velocity of the particle, at the given instant is called
b) tangential component
c) coriolis component
d) none of the mentioned

Answer: b [Reason:] The centripetal or radial component, is perpendicular to the velocity of the particle at the given instant. The tangential component, is parallel to the velocity of the particle at the given instant.

9. The component of the accelertion, perpendicular to the velocity of the particle, at the given instant is called
b) tangential component
c) coriolis component
d) none of the mentioned

Answer: a [Reason:] The centripetal or radial component, is perpendicular to the velocity of the particle at the given instant. The tangential component, is parallel to the velocity of the particle at the given instant.

10. A point B on a rigid link AB moves with respect to A with angular velocity ωrad/s. The total acceleration of B with respect to A will be equal to
a) vector sum of radial component and coriolis component
b) vector sum of tangential component and coriolis component
c) vector sum of radial component and tangential component
d) vector difference of radial component and tangential component

## Set 5

1. A type-writer constitutes a machine.
a) True
b) False

Answer: b [Reason:] When a mechanism is required to transmit power or to do some particular type of work, it then becomes a machine.But in case of a typewriter there is no case of power transmission. Hence it is not a machine.

2. The method of obtaining different mechanisms by fixing in turn different links in a kinematic chain, is known as
a) structure
b) machine
c) inversion
d) compound mechanism

Answer: c [Reason:] We can obtain as many mechanisms as the number of links in kinematic chain by fixing, in turn,different links in a kinematic chain. This method is known as inversion of the mechanism.

3. If the number of links in a mechanism are equal to l, then the number of possible inversions are equal to
a) l – 2
b) l – 1
c) l
d) l + 1

Answer: c [Reason:] Whatever is the number of links in a mechanism, only that much number of inversion can be obtained.

4. Which of the following statement is correct as regard to the difference between a machine and a structure?
a) The parts of a machine move relative to one another, whereas the members of a structure do not move relative to one another.
b) The links of a machine may transmit both power and motion, whereas the members of a structure transmit forces only.
c) A machine transforms the available energy into some useful work, whereas in a structure no energy is transformed into useful work.
d) all of the mentioned

5. A kinematic chain is known as a mechanism when
a) none of the links is fixed
b) one of the links is fixed
c) two of the links are fixed
d) none of the mentioned

Answer: b [Reason:] When one of the links of a kinematic chain is fixed, the chain is known as mechanism.

6. The inversion of a mechanism is
a) changing of a higher pair to a lower pair
b) turning its upside down
c) obtained by fixing different links in a kinematic chain
d) obtained by reversing the input and output motion

Answer: c [Reason:] We can obtain as many mechanisms as the number of links in kinematic chain by fixing, in turn,different links in a kinematic chain. This method is known as inversion of the mechanism.

7. The Grubler’s criterion for determining the degrees of freedom (n) of a mechanism having plane motion is
a) n = (l – 1) – j
b) n = 2(l – 1) – 2j
c) n = 3(l – 1) – 2j
d) n = 4(l – 1) – 3j

8. The mechanism forms a structure, when the number of degrees of freedom (n) is equal to
a) 0
b) 1
c) 2
d) -1

Answer: a [Reason:] A structure can be formed only when the number of degrees of freedom is zero.

9. In a four bar chain or quadric cycle chain
a) each of the four pairs is a turning pair
b) one is a turning pair and three are sliding pairs
c) two are turning pairs and two are sliding pairs
d) three are turning pairs and one is a sliding pair

Answer: a [Reason:] Four bar chain or quadric cycle chain consists of four links, each of them forms a turning pair.

10. The mechanism in which two are turning pairs and two are sliding pairs, is called a
a) double slider crank chain
b) elliptical trammel
c) scotch yoke mechanism
d) all of the mentioned