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# Multiple choice question for engineering

## Set 1

1. Which of the following disciplines provides study of inertia forces arising from the combined effect of the mass and motion of the parts?
a) theory of machines
b) applied mechanics
C) kinematics
d) kinetics

Answer: d [Reason:] The study of inertia forces arising from the combined effect of the mass and motion of the parts is called kinetics. The study of relative motion between the parts of a machine is called kinematics. The study of the relative motion between the parts of a machine and the forces acting on the parts is called theory of machines.

2. Which of the following disciplines provides study of relative motion between the parts of a machine?
a) theory of machines
b) applied mechanics
C) kinematics
d) kinetics

Answer: c [Reason:] The study of inertia forces arising from the combined effect of the mass and motion of the parts is called kinetics. The study of relative motion between the parts of a machine is called kinematics. The study of the relative motion between the parts of a machine and the forces acting on the parts is called theory of machines.

3. Which of the following disciplines provides study of the relative motion between the parts of a machine and the forces acting on the parts?
a) theory of machines
b) applied mechanics
C) kinematics
d) kinetics

Answer: a [Reason:] The study of inertia forces arising from the combined effect of the mass and motion of the parts is called kinetics. The study of relative motion between the parts of a machine is called kinematics. The study of the relative motion between the parts of a machine and the forces acting on the partsis called theory of machines.

4. The type of pair formed by two elements which are so connected that one is constrained to turn or revolve about a fixed axis of another element is known as
a) turning pair
b) rolling pair
c) sliding pair
d) spherical pair

Answer: a [Reason:] When two elements of a pair are connected in such a way that one can only turn or revolve about a fixed axis of another link, the pair is known as turning pair.

5. Which of the following is a lower pair?
a) ball and socket
b) piston and cylinder
c) cam and follower
d) both a and b

Answer: d [Reason:] In both ball and socket and piston cylinder there is surface contact between the two elements. Hence, they form a lower pair.

6. If two moving elements have surface contact in motion, such pair is known as
a) sliding pair
b) rolling pair
c) surface pair
d) lower pair

Answer: d [Reason:] when two elements of a pair have a surface contact when relative motion takes place and the surface of one element slides over the surface of the other, the pair formed is known as lower pair.

7. The example of lower pair is
a) shaft revolving in a bearing
b) straight line motion mechanisms
c) automobile steering gear
d) all of the mentioned

Answer: d [Reason:] In all the mentioned elements there is surface contact between the two elements. Hence, they form a lower pair.

8. Pulley in a belt drive acts as
a) cylindrical pair
b) turning pair
c) rolling pair
d) sliding pair

Answer: c [Reason:] When the two elements of a pair are connected in such a way that one rolls over another fixed link, the pair is known as rolling pair. In belt and pulley, the belt rolls over the pulley.

9. The example of rolling pair is
a) bolt and nut
b) lead screw of a lathe
c) ball and socket joint
d) ball bearing and roller bearing

Answer: d [Reason:] In ball bearing and roller bearing one element rolls over the other element. Hence, they are examples of rolling pair.

10. Any point on a link connecting double slider crank chain will trace a
a) straight line
b) circle
c) ellipse
d) parabola

Answer: c [Reason:] One of the inversions of a double slider crank chain is elliptical trammels. So, from the above given options ellipse is best suited.

11. The purpose of a link is to
a) transmit motion
c) act as a support
d) all of the mentioned

12. A universal joint is an example of
a) higher pair
b) lower pair
c) rolling pair
d) sliding pair

Answer: b [Reason:] In universal joint, there is surface contact between the two elements. Hence, they form a lower pair.

13. Rectilinear motion of piston is converted into rotary by
b) slider crank
c) connecting rod
d) gudgeon pin

Answer: b [Reason:] In single slider crank chain rotary motion is converted into reciprocating motion.

## Set 2

1. A jaw clutch is essentially a
a) positive action clutch
b) cone clutch
c) friction clutch
d) disc clutch

Answer: a [Reason:] The positive clutches are used when a positive drive is required. The simplest type of a positive clutch is a jaw or claw clutch.

2. The material used for lining of friction surfaces of a clutch should have _____________ coefficient of friction.
a) low
b) high
c) medium
d) none of the mentioned

Answer: b [Reason:] The material should have a high and uniform coefficient of friction.

3. The torque developed by a disc clutch is given by
a) T = 0.25 µ.W.R
b) T = 0.5 µ.W.R
c) T = 0.75 µ.W.R
d) T = µ.W.R

Answer: d [Reason:] T = µ.W.R where W = Axial force with which the friction surfaces are held together ; µ = Coefficient of friction ; and R = Mean radius of friction surfaces.

4. In case of a multiple disc clutch, if n1 are the number of discs on the driving shaft and n2 are the number of the discs on the driven shaft, then the number of pairs of contact surfaces will be
a) n1 + n2
b) n1 + n2 – 1
c) n1 + n2 + 1
d) none of the mentioned

Answer: b [Reason:] If n1 are the number of discs on the driving shaft and n2 are the number of the discs on the driven shaft, then the number of pairs of contact surfaces will be n1 + n2 – 1.

5. The cone clutches have become obsolete because of
a) small cone angles
b) exposure to dirt and dust
c) difficulty in disengaging
d) all of the mentioned

Answer: d [Reason:] A cone clutch, was extensively used in automobiles, but now-a-days it has been replaced completely by the disc clutch. In a cone clutch, the driver is keyed to the driving shaft by a sunk key and has an inside conical surface or face which exactly fits into the outside conical surface of the driven.

6. The axial force (We) required for engaging a cone clutch is given by
a) Wn sin α
b) Wn (sin α + µ cos α )
c) Wn (sin α + 0.25 µ cos α )
d) none of the mentioned

Answer: c [Reason:] Axial force required for engaging the clutch = Wn (sin α + 0.25 µ cos α ) where Wn = Normal force acting on the contact surfaces, α = Face angle of the cone, and µ = Coefficient of friction.

7. In a centrifugal clutch, the force with which the shoe presses against the driven member is the ___________ of the centrifugal force and the spring force.
a) difference
b) sum
c) ratio
d) none of the mentioned

Answer: a [Reason:] The force with which the shoe presses against the driven member is the difference of the centrifugal force and the spring force. The increase of speed causes the shoe to press harder and enables more torque to be transmitted.

8. Centrifugal clutches are designed to provide automatic and smooth engagement of load to driving member.
a) True
b) False

Answer: a [Reason:] Since the operating centrifugal force is a function of square of angular velocity, the friction torque for accelerating a load is also a function of square of speed driving member.

9. For a power screw having square threads with lead angle of 450 and coefficient of friction of 0.15 between screw and nut, the efficiency of the power screw, neglecting collar friction, is given by
a) 74%
b) 64%
c) 54%
d) 44%

Answer: a [Reason:] ȵ = tanα/tan(α + ɸ) ɸ = angle of friction, α = Helix angle or lead angle tanɸ = 0.15 ɸ = 8.530 ȵ = 74% .

## Set 3

1. The angle of inclination of the plane, at which the body begins to move down the plane, is called
a) angle of friction
b) angle of repose
c) angle of projection
d) none of the mentioned

Answer: a [Reason:] Consider that a body A of weight (W) is resting on a horizontal plane B. If a horizontal force P is applied to the body, no relative motion will take place until the applied force P is equal to the force of friction F, acting opposite to the direction of motion. The magnitude of this force of friction is F = μ.W = μ.RN, where RN is the normal reaction.

2. In a screw jack, the effort required to lift the load W is given by
a) P = W tan (α – φ)
b) P = W tan (α + φ)
c) P = W cos (α – φ)
d) P = W cos (α + φ)

Answer: b [Reason:] If one complete turn of a screw thread by imagined to be unwound, from the body of the screw and developed, it will form an inclined plane. P = W tan (α + φ) where α = Helix angle, and φ = Angle of friction.

3. The efficiency of a screw jack is given by
a) tan (α + φ)/tan α
b) tan α / tan (α + φ)
c) tan (α − φ)/ tan α
d) tan α/ tan (α − φ)

Answer: b [Reason:] Efficiency, η = Ideal effort/ Actual effort = P0 / P = W tanα/ W tan(α + φ) = tan α / tan (α + φ).

4. The radius of a friction circle for a shaft of radius r rotating inside a bearing is
a) r sin φ
b) r cos φ
c) r tan φ
d) r cot φ

Answer: a [Reason:] If a circle is drawn with centre O and radius OC = r sin φ, then this circle is called the friction circle of a bearing. The force R exerted by one element of a turning pair on the other element acts along a tangent to the friction circle.

5. The efficiency of a screw jack is maximum, when
a) α = 45º + φ/2
b) α = 45º – φ/2
c) α = 90º + φ
d) α = 90º − φ

Answer: b [Reason:] The efficiency of a screw jack is maximum when sin (2α + φ) is maximum, i.e. when α = 45º – φ/2.

6. The maximum efficiency of a screw jack is
a) 1 – sinφ/ 1 + sinφ
b) 1 + sinφ/ 1 – sinφ
c) 1 – tanφ/ 1 + tanφ
d) 1 + tanφ/ 1 – tanφ

Answer: a [Reason:] Maximum efficiency, ηmax = sin (90º – φ + φ) – sinφ/sin (90º – φ + φ) + sinφ = sin 90º – sin φ/sin 90º + sin φ = 1 – sinφ/ 1 + sinφ.

7. The frictional torque transmitted in a flat pivot bearing, considering uniform pressure, is
a) 1/2 × μ.W. R
b) 2/3 × μ.W. R
c) 3/4 × μ.W. R
d) μ.W.R

Answer: b [Reason:] Total frictional force = 2/3 × μ.W. R where μ = Coefficient of friction, W = Load over the bearing, and R = Radius of the bearing surface.

8. The frictional torque transmitted in a conical pivot bearing, considering uniform wear, is
a) 1/2 × μ.W. R cosec α
b) 2/3 × μ.W. R cosec α
c) 3/4 × μ.W. R cosec α
d) μ.W.R cosec α

Answer: a [Reason:] Total frictional torqur = 1/2 × μ.W. R cosec α where R = Radius of the shaft, and α = Semi-angle of the cone.

9. The frictional torque transmitted by a disc or plate clutch is same as that of
a) flat pivot bearing
b) flat collar bearing
c) conical pivot bearing
d) trapezoidal pivot bearing

10. The frictional torque transmitted by a cone clutch is same as that of
a) flat pivot bearing
b) flat collar bearing
c) conical pivot bearing
d) trapezoidal pivot bearing

11. In automobiles, Hooke’s joint is used between which of the following?
a) Clutch and gear box
b) Gear box and differential
c) Differential and wheels
d) Flywheel and clutch

Answer: b [Reason:] The main application of the universal or Hooke’s coupling is found in the transmission from the gear box to the differential or back axle of the automobiles. In such a case, we use two Hooke’s coupling, one at each end of the propeller shaft, connecting the gear box at one end and the differential on the other end.

12. Which of the following statements is not correct?
a) Hooke’s joint is used to connect two rotating co-planar, non-intersecting shafts
b) Hooke’s joint is used to connect two rotating co-planar, intersecting shafts
c) Oldham’s coupling is used to connect two parallel rotating shafts
d) Hooke’s joint is used in the steering mechanism for automobiles

13. A Hooke’s joint is used to connect two
a) coplanar and non-parallel shafts
b) non-coplanar and non-parallel shafts
c) coplanar and parallel shafts
d) non-coplanar and parallel shafts

Answer: b [Reason:] A Hooke’s joint is used to connect two shafts, which are intersecting at a small angle.

14. Two shafts with an included angle of 160° are connected by a Hooke’s joint. The driving shaft runs at a uniform speed of 1500 r.p.m. The driven shaft carries a flywheel of mass 12 kg and 100 mm radius of gyration. Find the maximum angular acceleration of the driven shaft.

Answer: a [Reason:] Given : α = 180° – 160° = 20°; N = 1500 r.p.m.; m = 12 kg ; k = 100 mm = 0.1 m We know that angular speed of the driving shaft, ω = 2 π × 1500 / 60 = 157 rad/s and mass moment of inertia of the driven shaft, I = m.k2 = 12(0.1)2 = 0.12 kg – m2

Let dω1 / dt = Maximum angular acceleration of the driven shaft, and θ = Angle through which the driving shaft turns. We know that, for maximum angular acceleration of the driven shaft,

cos 2θ = 2sin2α/2 – sin2α = 2sin220°/2 – sin220° = 0.124 2θ = 82.9° or θ = 41.45° and dω1 / dt = ω2cosα sin2θsin2α/(1 – cos2θsin2α)2 = 3090 rad/s2.

15. The angle between the axes of two shafts connected by Hooke’s joint is 18°. Determine the angle turned through by the driving shaft when the velocity ratio is maximum.
a) 90°
b) 180°
c) 270°
d) 360°

Answer: b [Reason:] Given : α = 98° Let θ = Angle turned through by the driving shaft. We know that velocity ratio, ω1/ω = cosα/1 – cos2θsin2α

The velocity ratio will be maximum when cos2 θ is minimum, i.e. when cos2 θ = 1 or when θ = 0° or 180°.

## Set 4

1. The minimum force required to slide a body of weight W on a rough horizontal plane is
a) W sinϴ
b) W cosϴ
c) W tanϴ
d) W cosecϴ

Answer: a [Reason:] The minimum force required to slide a body of weight W on a rough horizontal plane is W sinϴ. A body of weight W is required to move up the rough inclined plane whose angle of inclination with the horizontal is α. The effort applied parallel to the plane is given by P = W (sinα + μ cosα).

2. A body will begin to move down an inclined plane, if the angle of inclination of the plane is ____________ the angle of friction.
a) equal to
b) less than
c) greater than
d) none of the mentioned

3. A body of weight W is required to move up the rough inclined plane whose angle of inclination with the horizontal is α. The effort applied parallel to the plane is given by
a) P = W tanα
b) P = W tan (α + ɸ)
c) P = W (sinα + μ cosα)
d) P = W (cosα + μ sinα)

Answer: c [Reason:] The minimum force required to slide a body of weight W on a rough horizontal plane is W sinϴ. A body of weight W is required to move up the rough inclined plane whose angle of inclination with the horizontal is α. The effort applied parallel to the plane is given by P = W (sinα + μ cosα).

4. The coefficient of friction is the ratio of the limiting friction to the normal reaction between the two bodies.
a) True
b) False

Answer: a [Reason:] The coefficient of friction is defined as the ratio of the limiting friction(F) to the normal reaction(RN) between the two bodies. Mathematically, μ = F/RN.

5. In a screw jack, the effort required to lift the load W is given by
a) P = W tan (α – ɸ)
b) P = W tan (α + ɸ)
c) P = W tan (ɸ – α)
d) P = W cos (α + ɸ)

Answer: b [Reason:] The effort required at the circumference of the screw to lift the load W is given by P = W tan (α + ɸ) The effort required at the circumference of the screw to lower the load W is given by P = W tan (ɸ – α).

6. In a screw jack, the effort required to lower the load W is given by
a) P = W tan (α – ɸ)
b) P = W tan (α + ɸ)
c) P = W tan (ɸ – α)
d) P = W cos (α + ɸ)

Answer: c [Reason:] The effort required at the circumference of the screw to lower the load W is given by P = W tan (ɸ – α) The effort required at the circumference of the screw to lift the load W is given by P = W tan (α + ɸ).

7. The frictional torque for square thread at the mean radius r while raising load W is given by
a) T = W.rtan(α – ɸ)
b) T = W.rtan(α + ɸ)
c) T = W.rtanα
d) T = W.rtanɸ

8. Efficiency of a screw jack is given by
a) tan(α + ɸ)/tanα
b) tanα/ tan(α + ɸ)
c) tan(α – ɸ)/tanα
d) tanα/tan(α – ɸ)

9. The load cup of a screw jack is made separate from the head of the spindle to
a) enhance the load carrying capacity of the jack
b) reduce the effort needed for lifting the working load
c) reduce the value of frictional torque required to be countered for lifting the load
d) prevent the rotation of load being lifted

Answer: d [Reason:] In screw jack, the load to be raised or lowered, is placed on the head of the square threaded rod which is rotated by the application of an effort at the end of the lever for lifting or lowering the load.

10. The efficiency of the a screw jack is maximum, when
a) α = 450 + ɸ/2
b) α = 450 – ɸ/2
c) α = 900 + ɸ
d) α = 900 – ɸ

## Set 5

1. _____________ is the friction, experienced by a body, due to the motion of rotation as in case of foot step bearings.
a) Pivot friction
b) Solid friction
c) Dry friction
d) None of the mentioned

Answer: a [Reason:] Pivot friction is the friction, experienced by a body, due to the motion of rotation as in case of foot step bearings.

2. ______________ is the friction experienced between two dry and unlubricated surfaces in contact.
a) Pivot friction
b) Solid friction
c) Boundary friction
d) None of the mentioned

Answer: b [Reason:] The friction experienced between two dry and unlubricated surfaces in contact is known as dry or solid friction. It is due to the surface roughness.

3. ______________ is the friction, experienced between the rubbing surfaces, when the surfaces have a very thin layer of lubricant.
a) Pivot friction
b) Solid friction
c) Boundary friction
d) None of the mentioned

Answer: c [Reason:] Boundary friction It is the friction, experienced between the rubbing surfaces, when the surfaces have a very thin layer of lubricant. The thickness of this very thin layer is of the molecular dimension.

4. _____________ is the friction, experienced between the rubbing surfaces, when the surfaces have a thick layer of the lubricant.
a) Fluid friction
b) Solid friction
c) Boundary friction
d) None of the mentioned

Answer: a [Reason:] Fluid friction is the friction, experienced between the rubbing surfaces, when the surfaces have a thick layer of the lubricant. In this case, the actual surfaces do not come in contact and thus do not rub against each other.

5. _____________ is a measure of the resistance offered to the sliding one layer of the lubricant over an adjacent layer.
a) Viscocity
b) Density
c) Oiliness
d) None of the mentioned

Answer: a [Reason:] The viscosity is a measure of the resistance offered to the sliding one layer of the lubricant over an adjacent layer.

6. The absolute viscosity of a lubricant may be defined as the force required to cause a plate of unit area to slide with unit velocity relative to a parallel plate.
a) True
b) False

Answer: a [Reason:] The absolute viscosity of a lubricant may be defined as the force required to cause a plate of unit area to slide with unit velocity relative to a parallel plate, when the two plates are separated by a layer of lubricant of unit thickness.

7. The lubricant which gives ______________ force of friction is said to have greater oiliness.
a) greater
b) lesser
c) similar
d) none of the mentioned