Multiple choice question for engineering
Set 1
1. The included angle for the V-belt is usually
a) 20° – 30°
b) 30° – 40°
c) 40° – 60°
d) 60° – 80°
Answer
Answer: b [Reason:] The V-belts are made of fabric and cords moulded in rubber and covered with fabric and rubber. These belts are moulded to a trapezoidal shape and are made endless. These are particularly suitable for short drives. The included angle for the V-belt is usually from 30° to 40°.
2. The V-belts are particularly suitable for _____________ drives.
a) short
b) long
c) medium
d) none of the mentioned
Answer
Answer: a [Reason:] The V-belts are made of fabric and cords moulded in rubber and covered with fabric and rubber. These belts are moulded to a trapezoidal shape and are made endless. These are particularly suitable for short drives.
3. The groove angle of the pulley for V-belt drive is usually
a) 20° – 25°
b) 25° – 32°
c) 32° – 38°
d) 38° – 45°
Answer
Answer: c [Reason:] A small groove angle will require more force to pull the belt out of the groove which will result in loss of power and excessive belt wear due to friction and heat. Hence the selected groove angle is a compromise between the two. Usually the groove angles of 32° to 38° are used.
4. A V-belt designated by A-914-50 denotes
a) a standard belt
b) an oversize belt
c) an undersize belt
d) none of the mentioned
Answer
Answer: a [Reason:] a V-belt marked A – 914 – 50 denotes a standard belt of inside length 914 mm and a pitch length 950 mm. A belt marked A – 914 – 52 denotes an oversize belt by an amount of (52 – 50) = 2 units of grade number.
5. The wire ropes make contact at
a) bottom of groove of the pulley
b) sides of groove of the pulley
c) sides and bottom of groove of the pulley
d) any where in the groove of the pulley
Answer
Answer: a [Reason:] The wire ropes run on grooved pulleys but they rest on the bottom of the grooves and are not wedged between the sides of the grooves.
6. Which of the following statements are correct regarding power transmission through V-belts?
(i) V-belts are used at the high-speed end.
(ii) V-belts are used at the low-speed end.
(iii) V-belts are of standard lengths.
(iv) V-angles of pulleys and belts are standardized.
Select the correct answer using the code given below.
a) 1 and 3 only
b) 2 and 4 only
c) 2, 3 and 4
d) 1, 3 and 4
Answer
Answer: d [Reason:] Advantages of V -belts
V-belts are used at the high-speed end.
(i) V-belts are used at the high-speed end.
(ii) V-belts are of standard lengths.
(iii) V-angles of pulleys and belts are standardized
7. The creep in a belt drive is due to the
a) material of the pulleys
b) material of the belt
c) unequal size of the pulleys
d) unequal tension in tight and slack sides of the belt
Answer
Answer: d [Reason:] The belt always has an initial tension when installed over the pulleys. This initial tension is same throughout the belt length when there is no motion. During rotation of the drive, tight side tension is higher than the initial tension and slack side tension is lower than the initial tension.
8. In order to have a good grip on the pulley, the V-belt should touch the bottom of the groove in the pulley.
a) True
b) False
Answer
Answer: b [Reason:] The V-belt may be operated in either direction with tight side of the belt at the top or bottom. The centre line may be horizontal, vertical or inclined.
Set 2
1. The lengths of the links of a 4- bar linkage with revolute pairs only are p,q,r and s units. Given that p < q < r < s and s+p < q+r which of these links should be the fixed one, for obtaining a ‘double crank’ mechanism?
a) ink of length p
b) link of length q
c) link of length r
d) link of length s
Answer
Answer: a [Reason:] For Double crank mechanism Shortest link is fixed.
Here shortest link is ‘P’.
2. For a four-bar linkage in toggle position, the value of mechanical advantage is
a) 0.0
b) 0.5
c) 1.0
d) ∞
Answer
Answer: d [Reason:] At Toggle position output velocity is zero
And hence, mechanical advantage = input velocity/output velocity = ∞.
3. In a slider-crank mechanism, the crank is rotating with an angular velocity of 20 rad/s in counterclockwise direction. At the instant when the crank is perpendicular to the direction of the piston movement, velocity of the piston is 2 m/s. Radius of the crank is
a) 100 cm
b) 10 cm
c) 1 cm
d) 0.1 cm
Answer
Answer: b [Reason:] Vp = ωr(sinϴ + sin2ϴ/2n)
In this case ϴ = 900
Vp = ωr
r = Vp/ω = 2/20 = 0.1 m or 10 cm.
4. In a single link robotic arm the end-effector slides upward along the link with a velocity of 0.5 m/s while the link rotates about revolute joint with an angular speed of 1 rad/sec. When the end-effector is at a distance of 1 m from the joint, the acceleration experienced by the end-effector will be
a) 1 m/s2
b) 1.41 m/s2
c) 1.71 m/2
d) 2 m/2
Answer
Answer: a [Reason:] a = 2ωV = 2 x 1 x 0.5 = 1 m/s2.
5. For the same crank length and uniform angular velocity of the crank in an offset slider crank mechanism, if the connecting rod length is increased by 1.5 times, the velocity of piston will
a) remain unchanged
b) increase 1.5 times
c) decrease by 1.5 times
d) increase by 1.5√2 times
Answer
Answer: c [Reason:] V1 = ωr(sinϴ + sin2ϴ/2n)
V2 = ωr(sinϴ + sin2ϴ/3n)
from these two equation, V2 < V1
V2 will decrease but correct quantification can not be done with available data.
Among the available options, best answer is (c).
6. It is planned to construct a four-bar mechanism ABCD with length AB= 60mm, BC = 100mm, CD = 70 mm and fixed link AD = 200 mm. If at least one link is required to have a complete rotation, this mechanism is
a) of crank-rocker type
b) of double-crank type
c) of double rocker type
d) impossible to construct
Answer
Answer: c [Reason:] S + L = 60 + 200 = 260 mm
P + Q = 100 + 70 = 170 mm
From grashoff equality when S + L > P + Q
So always double rocker.
7. The number of links in a planer mechanism with revolute joints having 10 instantaneous centres is
a) 3
b) 4
c) 5
d) 6
Answer
Answer: c [Reason:] n(n – 1)/2 = 10
n(n – 1) = 20
n = 5.
8. A weston differential pulley block consists of a lower block and upper block. The upper block has two cogged grooves, one of which has a radius of 150 mm and the other a radius of 125 mm. If the efficiency of the machine is 50% calculate the effort required to raise a load of 1.5 kN.
a) 250 N
b) 300 N
c) 350 N
d) 400 N
Answer
Answer: a [Reason:] We know that in case of a Weston differential pulley block,
V.R. = 2D/D – d = 2 x 300/300 -250 = 12
Using the relation, Efficiency = M.A./V.R. x 100
or, 50 = M.A./12 x 100
M.A. = 6
Again, M.A. = W/P
6 = 1.5 x 1000/ P
P = 250 N.
9. Following are the specifications of a single purchase crab:
Diameter of load drum, d = 200 mm
Length of lever, l = 1.2 m
No. of teeth on pinion, T1 = 10
No. of teeth on spur wheel, T2 = 100
Find the velocity ratio of this machine.
a) 100
b) 110
c) 120
d) 130
Answer
Answer: c [Reason:] V.R. = 2l/d x T2/T1
= 2 x 120/20 x 100/10 = 120.
10. On a machine efforts of 100 N and 160 N are required to lift the loads of 3000 N and 9000 N respectively. Find the law of the machine.
a) P = 1/100W + 60
b) P = 1/100W + 70
c) P = 1/100W + 80
d) P = 1/100W + 90
Answer
Answer: c [Reason:] Let the law of machine be P = mW + C
where P = effort applied, W = load lifted and m and C being constants.
when P = 100 N W = 3000 N
when P = 160 N W = 9000 N
Putting these values in the law of machine.
100 = 3000m + C …………(i)
160 = 9000m + C …………(ii)
Subtracting (i) and (ii), we get
60 = 6000 m
or, m = 1/100
Putting this value in equation (i), we get
100 = 3000 x 1/100 + C
C = 70
Hence, the machine follows the laws
P = 1/100W +70.
11. Following are the specifications of a single purchase crab:
Diameter of load drum, d = 200 mm
Length of lever, l = 1.2 m
No. of teeth on pinion, T1 = 10
No. of teeth on spur wheel, T2 = 100
On this machine efforts of 100 N and 160 N are required to lift the loads of 3000 N and 9000 N respectively. Find the efficiency at 3000N.
a) 10 %
b) 15 %
c) 20 %
d) 25 %
Answer
Answer: d [Reason:] V.R. = 2l/d x T2/T1
= 2 x 120/20 x 100/10 = 120
M.A. = W/P = 3000/100 = 30
Efficiency = M.A./V.R. = 30/120 = 0.25 = 25%.
12. Following are the specifications of a single purchase crab:
Diameter of load drum, d = 200 mm
Length of lever, l = 1.2 m
No. of teeth on pinion, T1 = 10
No. of teeth on spur wheel, T2 = 100
On this machine efforts of 100 N and 160 N are required to lift the loads of 3000 N and 9000 N respectively. Find the efficiency at 9000N.
a) 30 %
b) 40 %
c) 46.8 %
d) 56.8 %
Answer
Answer: d [Reason:] V.R. = 2l/d x T2/T1
= 2 x 120/20 x 100/10 = 120
M.A. = W/P = 9000/160 = 900/16
Efficiency = M.A./V.R. = 900/16 x 120 = 0.468 = 46.8%.
Set 3
1. The coriolis component of acceleration exists whenever a point moves along a path that has
a) linear displacement
b) rotational motion
c) gravitational acceleration
d) tangential acceleration
Answer
Answer: b [Reason:] When a point on one link is sliding along another rotating link such as in quick return motion mechanism, then Coriolis component of acceleration must be taken into account. It means for Coriolis component, rotational motion is required.
2. In a pantograph, all the pairs are
a) turning pairs
b) sliding pairs
c) spherical pairs
d) self-closed pairs
Answer
Answer: a [Reason:] Pantograph is an instrument used to reproduce to an enlarged or a reduced scale and as exactly as possible the path described by a given point. It consists of bars connected by turning pairs.
3. Which of the following mechanism is made up of turning pairs?
a) Scott Russel’s mechanism
b) Peaucellier’s mechanism
c) Hart’s mechanism
d) All of the mentioned
Answer
Answer: b and c [Reason:] Exact straight line motion mechanisms are made up of turning pairs. These mechanisms are as follows:
a) Peaucellier’s mechanism
b) Hart’s mechanism.
4. Scott Russel’s mechanism is made up of sliding pair.
a) True
b) False
Answer
Answer: a [Reason:] Exact straight line motion mechanisms consists of one sliding pair. The Scott Russell’s mechanism is of this type.
5. An exact straight line motion mechanism is a
a) Scott-Russell’s mechanism
b) Hart’s mechanism
c) Peaucellier’s mechanism
d) All of the mentioned
Answer
Answer: d [Reason:] All the mechanisms mentioned above consists of exact straight line motion. Scott-Russell’s mechanism consists of sliding pair whereas Peaucellier’s mechanism and Hart’s mechanism consists of turning pair.
6. Which of the following mechanism is an approximate straight line motion mechanism?
a) Watt’s mechanism
b) Grasshopper mechanism
c) Robert’s mechanism
d) All of the mentioned
Answer
Answer: d [Reason:] The mechanism that are approximate straight line motion are as follows:
a) Watt’s mechanism
b) Scott-Russell’s mechanism
c) Grasshopper mechanism
d) Robert’s mechanism
e) Tehebicheff’s mechanism.
7. The fundamental equation for correct steering is
a) sinɸ + sinα = b/c
b) cosɸ – sinα = c/b
c) cotɸ – cotα = c/b
d) tanɸ + cotα = b/c
Answer
Answer: c [Reason:] The condition for correct steering is that all the four wheels must turn about the same instantaneous centre.
The fundamental equation for correct steering is
cotɸ – cotα = c/b
where ɸ and α = Angle through which the axix of the outer wheel and inner wheel turns respectively
c = Distance between the pivots of the front axles
b = Wheel base.
8. The condition for correct steering of a Davis steering is
a) sinα = b/c
b) cosα = c/b
c) tanα = c/2b
d) cotα = c/2b
Answer
Answer: c [Reason:] In case of Davis steering gear, the condition for correct steering is
tanα = c/2b
where α = Angle of inclination of the links to the vertical.
9. The driving and driven shafts connected by a Hooke’s joint will have equal speeds, if
a) cosϴ = sinα
b) sinϴ = √tanα
c) tanϴ = √cosα
d) cotϴ = cosα
Answer
Answer: c [Reason:] A Hooke’s joint is used to connect two shafts, which are intersecting at a small angle. The speed of the driving and driven shafts will be equal, when
tanϴ = √cosα.
10. The Ackerman steering gear mechanism is preferred to the Davis steering gear mechanism because
a) whole of the mechanism in the Ackerman steering gear is on the back of the front wheels
b) the Ackerman steering gear consists of turning pairs
c) the Ackerman steering gear is most economical
d) both a and b
Answer
Answer: d [Reason:] The Acerman steering gear mechanism is much simpler than Davis gear. The whole mechanism of Ackerman steering gear is on the back of the front wheels, whereas in Davis steering gear, it is in front of the wheels. The Ackerman steering gear consists of turning pairs, whereas Davis steering gear consists of sliding members.
Set 4
1. The instantaneous centre is a point which is always fixed.
a) True
b) False
Answer
Answer: b [Reason:] The instantaneous center is not always fixed.
2. The angular velocity of a rotating body is expressed in terms of
a) revolution per minute
b) radians per second
c) any one of the mentioned
d) none of the mentioned
Answer
Answer: c [Reason:] Angular velocity is expressed both as revolution per minute and radians per second.
3. The linear velocity of a rotating body is given by the relation
a) v = rω
b) v = r/ω
c) v = ω/r
d) v = ω2/r
Answer
Answer: a [Reason:] The linear velocity of a rotating body is given by the relation v = rω
The linear acceleration of a rotating body is given by the relation a = rα.
4. The linear acceleration of a rotating body is given by the relation
a) a = rα
b) a = r/α
c) a = α/r
d) a = α2/r
Answer
Answer: a [Reason:] The linear velocity of a rotating body is given by the relation v = rω
The linear acceleration of a rotating body is given by the relation a = rα.
5. The relation between linear velocity and angular velocity of a cycle
a) exists under all conditions
b) does not exist under all conditions
c) exists only when it does not slip
d) exists only when it moves on horizontal plane
Answer
Answer: a
6. The velocity of piston in a reciprocating pump mechanism depends upon
a) angular velocity of the crank
b) radius of the crank
c) length of the connecting rod
d) all of the mentioned
Answer
Answer: d
7. The linear velocity of a point B on a link rotating at an angular velocity ω relative to another point A on the same link is
a) ω2AB
b) ωAB
c) ω(AB)2
d) ω/AB
Answer
Answer: b
8. The linear velocity of a point relative to another point on the same link is ……….. to the line joining the points.
a) perpendicular
b) parallel
c) at 450
d) none of the mentioned
Answer
Answer: a [Reason:] The total linear acceleration of a particle can be obtained by combining the two mutually perpendicular accelerations.
9. According to Kennedy’s theorem the instantaneous centres of three bodies having relative motion lie on a
a) curved path
b) straight line
c) point
d) none of the mentioned
Answer
Answer: b [Reason:] The Aronhold Kennedy’s theorem states that if three bodies move relatively to each other, they have three instantaneous centres and lie on a straight line.
10. The instantaneous centers of a slider moving in a linear guide lies at
a) pin joints
b) their point of contact
c) infinity
d) none of the mentioned
Answer
Answer: c [Reason:] The instantaneous centers of a slider moving in a linear guide lies at infinity.
The instantaneous centers of a slider moving in a curved surface lies at the center of curvature.
Set 5
1. When bevel gears having equal teeth and equal pitch angles connect two shafts whose axes intersect at right angle, then they are known as
a) angular bevel gears
b) crown bevel gears
c) internal bevel gears
d) mitre gears
Answer
Answer: d [Reason:] When equal bevel gears (having equal teeth and equal pitch angles) connect two shafts whose axes intersect at right angle, then they are known as mitre gears.
When the bevel gears connect two shafts whose axes intersect at an angle other than a right angle, then they are known as angular bevel gears.
2. The face angle of a bevel gear is equal to
a) pitch angle – addendum angle
b) pitch angle + addendum angle
c) pitch angle – dedendum angle
d) pitch angle + dedendum angle
Answer
Answer: b [Reason:] Face angle is the angle subtended by the face of the tooth at the cone centre. It is denoted by ‘φ’. The face angle is equal to the pitch angle plus addendum angle.
3. The root angle of a bevel gear is equal to
a) pitch angle – addendum angle
b) pitch angle + addendum angle
c) pitch angle – dedendum angle
d) pitch angle + dedendum angle
Answer
Answer: c [Reason:] Root angle is the angle subtended by the root of the tooth at the cone centre. It is denoted by ‘θR’. It is equal to the pitch angle minus dedendum angle.
4. If b denotes the face width and L denotes the cone distance, then the bevel factor is written as
a) b / L
b) b / 2L
c) 1 – 2 b.L
d) 1 – b / L
Answer
Answer: d [Reason:] Bevel factor = 1 – b / L.
5. For a bevel gear having the pitch angle θ, the ratio of formative number of teeth (TE) to actual number of teeth (T) is
a) 1/sin θ
b) 1/cos θ
c) 1/tan θ
d) sin θ cos θ
Answer
Answer: b [Reason:] (TE)/T = 1/cos θ.
6. The worm gears are widely used for transmitting power at ______________ velocity ratios between non-intersecting shafts.
a) high
b) low
c) medium
d) none of the mentioned
Answer
Answer: a [Reason:] The worm gears are widely used for transmitting power at high velocity ratios between non-intersecting shafts that are generally, but not necessarily, at right angles.
7. In worm gears, the angle between the tangent to the thread helix on the pitch cylinder and the plane normal to the axis of worm is called
a) pressure angle
b) lead angle
c) helix angle
d) friction angle
Answer
Answer: b [Reason:] Lead angle is the angle between the tangent to the thread helix on the pitch cylinder and the plane normal to the axis of the worm. It is denoted by λ.
8. The normal lead, in a worm having multiple start threads, is given by
a) lN = l / cos λ
b) lN = l . cos λ
c) lN = l
d) lN = l tan
Answer
Answer: b [Reason:] The term normal pitch is used for a worm having single start threads. In case of a worm having multiple start threads, the term normal lead (lN) is used, such that
lN = l . cos λ
where lN = Normal lead,
l = Lead, and
λ = Lead angle.
9. The number of starts on the worm for a velocity ratio of 40 should be
a) single
b) double
c) triple
d) quadruple
Answer
Answer: a [Reason:] For number of starts from 36 and above we have single velocity ratio. For 12 to 36 we have double velocity ratio, for 8 to 12, we have triple velocity ratio and for 6 to 12 we have quadruple velocity ratio.
10. The axial thrust on the worm (WA) is given by
a) WA = WT . tan φ
b) WA = WT / tan φ
c) WA = WT . tan λ
d) WA = WT / tan λ
Answer
Answer: d [Reason:] Axial force or thrust on the worm,
WA = WT / tan λ = Tangential force on the worm gear
where WT = Tangential force acting on the worm,
φ = Pressure angle, and
λ = Lead angle.