Mechanical Engineering
Dynamics of Machines
Multiple choices Question
1. 1. When
the crank is at the inner dead centre, in a horizontal reciprocating steam
engine, then the velocity of the piston will be
(a)
zero
(b) minimum
(c) maximum
2. 2.The
acceleration of the piston in a reciprocating steam engine is given by
where ω = Angular velocity of the
crank,
r = Radius of the crank,
θ = Angle turned by the crank from
inner dead centre, and
n = Ratio of length of connecting
rod to crank radius.
Ans : (D)
1. 3. A
rigid body, under the action of external forces, can be replaced by two masses
placed at a fixed distance apart. The two masses form an equivalent dynamical
system, if
(a)
the sum of two masses is equal to the total mass of the body
(b)
the centre of gravity of the two masses coincides with that of the body
(c)
the sum of mass moment of inertia of the masses about their centre of gravity
is equal to the mass moment of inertia of the body
(d) all of the above
1. 4. The
essential condition of placing the two masses, so that the system becomes
dynamically equivalent is
(a) l1 .l2 = kG2
(b) l1 .l2 = kG
(c) l1
= kG
(d) l2 = kG
where l1 and l2 = Distance of two
masses from the centre of gravity of the body, and
kG = Radius of gyration of the body.
2. 5. In
an engine, the work done by inertia forces in a cycle is
(a) positive
(b)
zero
(c)
negative
(d)
none of these
1. 6.The
maximum fluctuation of energy is the
(a)
sum of maximum and minimum energies
(b) difference between
the maximum and minimum energies
(c)
ratio of the maximum energy and minimum energy
(d)
ratio of the mean resisting torque to the work done per cycle
2. 7..In
a turning moment diagram, the variations of energy above and below the mean
resisting torque line is called
(a) fluctuation of
energy
(b)
maximum fluctuation of energy
(c)
coefficient of fluctuation of energy
(d)
none of the above
3. 8. The
ratio of the maximum fluctuation of speed to the mean speed is called
(a)
fluctuation of speed
(b)
maximum fluctuation of speed
(c) coefficient of
fluctuation of speed
(d)
none of these
4. 9. The
ratio of the maximum fluctuation of energy to the, ......... is called
coefficient of fluctuation of energy.
(a)
minimum fluctuation of energy
(b) work done per cycle
1. 10. The
maximum fluctuation of energy in a flywheel is equal to
Ans : (D)
11. Force which
does not act on the connecting rod is ______
a) Weight of connecting rod
b) Inertia force of connecting rod
c) Radial force
d) Coriolis force
12. Inertia
forces on the reciprocating parts acts along the line of stroke.
a) True
b) False
13. When mass of the reciprocating parts is
neglected then the inertia force is _____
a) Maximum
b) Minimum
c) 0
d) Not defined
14. For a steam
engine, the following data is given:
Piston diameter = 0.24 m, length of stroke = 0.6 m, length of connecting rod =
1.5 m, mass of reciprocating parts = 300 kg, mass of connecting rod = 250 kg;
speed of rotation = 125 r.p.m ; centre of gravity of connecting rod from crank
pin = 0.5 m ; Kg of the connecting rod about an axis through the centre of
gravity = 0.65 m
calculate inertia force at θ=30 degrees from IDC.
a) 19000 N
b) 19064 N
c) 19032 N
d) 20064 N
15. Piston
diameter = 0.24 m, length of stroke = 0.6 m, length of connecting rod = 1.5 m,
mass of reciprocating parts = 300 kg, mass of connecting rod = 250 kg; speed of
rotation = 125 r.p.m; centre of gravity of connecting rod from crank pin = 0.5
m ; Kg of the connecting rod about an axis through the centre of gravity = 0.65
m
Find the equivalent length L of a simple pendulum swung about an axis.
a) 1.35 m
b) 1.42 m
c) 1.48 m
d) 1.50 m
16. From the
data given:
Piston diameter = 0.24 m, length of stroke = 0.6 m, length of connecting rod =
1.5 m, mass of reciprocating parts = 300 kg, mass of connecting rod = 250 kg;
speed of rotation = 125 r.p.m ; centre of gravity of connecting rod from crank
pin = 0.5 m ; Kg of the connecting rod about an axis through the centre of
gravity = 0.65 m
Find the correcting couple in N-m?
a) 52.7
b) 49.5
c) 59.5
d)56.5
17. Piston
diameter = 0.24 m, length of stroke = 0.6 m, length of connecting rod = 1.5 m,
mass of reciprocating parts = 300 kg, mass of connecting rod = 250 kg; speed of
rotation = 125 r.p.m; centre of gravity of connecting rod from crank pin = 0.5
m ; Kg of the connecting rod about an axis through the centre of gravity = 0.65
m
Find angular acceleration of connecting rod in rad/s2.
a) 16.782
b) 17.824
c) 15.142
d) 17.161
18. Torque due to weight of the connecting rod
affects the torque due to connecting rod.
a) True
b) False
19.In the figure given below, the quantity represented by the arrow is known as ___________
a) Maximum
Torque
b) Minimum Torque
c) Maximum Force
d) Mean resisting torque
20. Turning
moment is maximum when the crank angle is 90 degrees.
a) True
b) False
21.The curve abc in figure below is known as _________
b) Outstroke
c) Positive couple
d) Negative couple
a) Instroke
b) Outstroke
c) Positive couple
28. The maximum fluctuation of energy is the
30. Which of the following statement is wrong?
a) The difference between the maximum and minimum energies is called maximum
fluctuation of energy.
b) The co-efficient of fluctuation of speed is the ratio of maximum fluctuation
of speed to the mean speed.
c) The variations of energy above and below the mean resisting torque line is
known as fluctuation of energy.
d) None of the mentioned
Unit 2 - Balancing
1. The
balancing of rotating and reciprocating parts of an engine is necessary when it
runs at
(a) slow speed
(b)
medium speed
(c) high speed
2. A
disturbing mass m1 attached to a rotating shaft may be balanced by a single
mass m2 attached in the same plane of rotation as that of m1 such that
(a) m1.r2 = m2.r1
(b) m1.r1 = m2.r2
(c) m1. m2 = r1.r2
3. For
static balancing of a shaft,
(a)
the net dynamic force acting on the shaft is equal to zero
(b) the net couple due to the dynamic
forces acting on the shaft is equal to zero
(c) both (a) and (b)
(d) none of the above
4. For
dynamic balancing of a shaft,
(a)
the net dynamic force acting on the shaft is equal to zero
(b)
the net couple due to dynamic forces acting on the shaft is equal to zero
(c) both (a) and (b)
(d)
none of the above
5. In
order to have a complete balance of the several revolving masses in different
planes
(a) the resultant force must be zero
(b) the resultant couple must be zero
(c)
both the resultant force and couple must be zero
(d) none of the above
6. The
primary unbalanced force is maximum when the angle of inclination of the crank
with the line of stroke is
(a) 0°
(b) 90°
(c)
180°
(d) 360°
7. The
partial balancing means
(a)
balancing partially the revolving masses
(b)
balancing partially the reciprocating masses
(c) best balancing of engines
(d) all of the above
8. In
order to facilitate the starting of locomotive in any position, the cranks of a
locomotive, with two cylinders, are placed at . . . . . . to each other.
(a) 45°
(b)
90°
(c) 120°
(d) 180°
9. In
a locomotive, the ratio of the connecting rod length to the crank radius is
kept very large in order to
(a) minimise the effect of primary
forces
(b)
minimise the effect of secondary forces
(c) have perfect balancing
(d) start the locomotive quickly
10. If
c be the fraction of the reciprocating parts of mass m to be balanced per
cylinder of a steam locomotive with crank radius r, angular speed ω, distance
between centre lines of two cylinders a, then the magnitude of the maximum
swaying couple is given b
Ans
: (B)
11. The
swaying couple is maximum or minimum when the angle of inclination of the crank
to the line of stroke ( θ ) is equal to
(a)
45° and 135°
(b)
90° and 135°
(c)
135° and 225°
(d) 45° and 225°
12. The
tractive force is maximum or minimum when the angle of inclination of the crank
to the line of stroke ( θ ) is equal to
(a)
90° and 225°
(b)
135° and 180°
(c)
180° and 225°
(d) 135° and 315°
13. The
swaying couple is due to the
(a) primary unbalanced
force
(b)
secondary unbalanced force
(c)
two cylinders of locomotive
(d)
partial balancing
14. In
a locomotive, the maximum magnitude of the unbalanced force along the
perpendicular to the line of stroke, is known as
(a
) tractive force
(b)
swaying couple
(c) hammer blow
(d)
none of these
15. The
effect of hammer blow in a locomotive can be reduced by
(a)
decreasing the speed
(b)
using two or three pairs of wheels coupled together
(c)
balancing whole of the reciprocating parts
(d) both (a) and (b)
16. Multi-cylinder
engines are desirable because
(a)
only balancing problems are reduced
(b)
only flywheel size is reduced
(c) both (a) and (b)
(d)
none of these
17. When
the primary direct crank of a reciprocating engine makes an angle θ with the
line of stroke, then the secondary direct crank will make an angle of . . . . .
with the line of stroke.
(a)
θ /2
(b)
θ
(c)2θ
(d)4θ
18. Secondary
forces in reciprocating mass on engine frame are
(a)
of same frequency as of primary forces
(b) twice the frequency
as of primary forces
(c)
four times the frequency as of primary forces
(d)
none of the above
19. The
secondary unbalanced force produced by the reciprocating parts of a certain
cylinder of a given engine with crank radius r and connecting rod length l can
be considered as equal to primary unbalanced force produced by the same weight
having
(a) an equivalent crank
radius r2/4l and rotating at twice the speed of the engine
(b)
r2/4l as equivalent crank radius and rotating at engine speed
(c)
equivalent crank length of r2/4l and rotating at engine speed
(d)
none of the above
20. Which
of the following statement is correct?
(a)
In any engine, 100% of the reciprocating masses can be balanced dynamically
(b)
In the case of balancing of multicylinder engine, the value of secondary force
is higher than the value of the primary force
(c) In the case of
balancing of multi mass rotating systems, dynamic balancing can be directly
started without static balancing done to the system
(d)
none of the above.
Unit 3 - Free Vibration
1. 1. When there is a reduction in amplitude
over every cycle of vibration, then the body is said to have
(a) free vibration
(b) forced vibration
(c)
damped vibration
2. 2..Longitudinal vibrations are said to
occur when the particles of a body moves
(a) perpendicular to its axis
(b)
parallel to its axis
(c) in a circle about its axis
3. 3.When a body is subjected to transverse
vibrations, the stress induced in a body will be
(a) shear stress
(b)
tensile stress
(c) compressive stress
4. 4. The natural frequency (in Hz) of free
longitudinal vibrations is equal to
Ans : (D)
5. The factor which affects the critical speed of a shaft is
(a) diameter of the disc
(b) span of the shaft
(c) eccentricity
(d)
all of these
2. 6. The equation of motion for a vibrating
system with viscous damping is
If the roots of this equation are real, then the system will be
(a)
over damped
(b) under damped
(c) critically damped
3. 7. In under damped vibrating system, if x1
and x2 are the successive values of the amplitude on the same side of the mean position,
then the logarithmic decrement is equal to
Ans
: (B)
1. 8.The ratio of the maximum displacement of
the forced vibration to the deflection due to the static force, is known as
(a)
damping factor
(b) damping coefficient
(c)
logarithmic decrement
(d)
magnification factor
2. 9. In vibration isolation system, if / n ωω
is less than 2 , then for all values of the damping factor, the
transmissibility will be
(a) less than unity
(b)
equal to unity
(c) greater than unity
(d)
zero
where
ω = Circular frequency of the system in rad/s, and
ωn = Natural circular frequency of
vibration of the system in rad/s. 10.
3. 10. In vibration isolation system, if ω/ωn
> 1, then the phase difference between the transmitted force and the
disturbing force is
(a) 0°
(b) 90°
(c)
180°
(d) 270°
b) Elastic points
c) Inelastic points
d) Breaking points
12. In a three
rotor system, free torsional vibration cannot occur if there is only one node.
a) True
b) False
13. In which of
the following condition torsional vibration will not take place, considering 3
rotors A, B and C. A is rotating in clockwise direction.
a) B in clockwise C in anticlockwise
b) C in clockwise B in anticlockwise
c) B and C in clockwise
d) B and C in anticlockwise
14. For
occurrence of free torsional vibration in a three rotor system which of the
condition is necessary?
a) Rotors moving in same direction
b) Rotors having same frequency
c) Rotors having different frequency
d) Rotors rotate in the same sense
a) Increases 4 times
b) Increases 2 times
c) Decreases 4 times
d) Decreases 2 times
b) Two rotor system
c) Three rotor system
d) Four rotor system
19.For a three rotor system in the figure given below, the length of one shaft(P) is twice the other(Q), then what is the relation between the Mass moment of inertia of the shafts.
b) I(P) = 2I(Q)
c) I(P) = I(Q)
d) 2I(P) = 3I(Q)
Unit 4 - Forced Vibration
6. The equation of motion for a vibrating system with viscous damping is
9. In vibration isolation system, if ω/ωn is less than √2 , then for all values of the damping factor, the transmissibility will be
Unit 5 - Mechanism for control
1. 1. The height of a Watt’s governor (in
metres) in equal to
(a) 8.95/N2
(b) 89.5/N2
(c)
895/N2
(d) 8950/N2
where N = Speed of the arm and ball about the
spindle axis.
2. 2. The ratio of the height of a Porter
governor (when the length of arms and links are equal) to the height of a
Watt’s governor is
Ans
:(C)
1. 3. When the sleeve of a Porter governor
moves upwards, the governor speed
(a)
increases
(b) decreases
(c) remains unaffected
2. 4. A Hartnell governor is a
(a) pendulum type governor
(b)
spring loaded governor
(c) dead weight governor
(d) inertia governor
3. 5. Which of the following governor is used
to drive a gramophone ?
(a) Watt governor
(b) Porter governor
(c)
Pickering governor
(d) Hartnell governor
4. 6. Which of the following is a spring
controlled governor?
(a) Hartnell
(b) Hartung
(c) Pickering
(d)
all of these
5. 7. For two governors A and B, the lift of
sleeve of governor A is more than that of governor B, for a given fractional
change in speed. It indicates that
(a)
governor A is more sensitive than governor B
(b) governor B is more sensitive than
governor A
(c) both governors A and B are equally
sensitive
(d) none of the above
6. 8. The sensitiveness of a governor is given
by
Ans:
(B)
1. 9. In a Hartnell governor, if a spring of
greater stiffness is used, then the governor will be
(a) more sensitive
(b)
less sensitive
(c) isochronous
2. 10. A governor is said to be hunting, if the
speed of the engine
(a) remains constant at the mean speed
(b) is above the mean speed
(c) is below the mean speed
(d)
fluctuates continuously above and below the mean speed.
3. 11. A hunting governor is
(a) more stable
(b) less sensitive
(c)
more sensitive
(d) none of these
4. 12. Isochronism in a governor is desirable
when
(a) the engine operates at low speeds
(b) the engine operates at high speeds
(c) the engine operates at variable
speeds
(d)
one speed is desired under one load
5. 13. The power of a governor is equal to
Ans: (D)
1. 14. When the relation between the
controlling force (FC ) and radius of rotation (r) for a spring controlled
governor is FC = a.r + b, then the
governor will be
(a)
stable
(b) unstable
(c)
isochronous
2. 15. For a governor, if FC is the controlling
force, r is the radius of rotation of the balls, the stability of the governor
will be ensured when
Ans:
(A)
1. 16.A disc is spinning with an angular
velocity ω rad/s about the axis of spin. The couple applied to the disc causing
precession will be
Ans
:(D)
1. 17. A disc spinning on its axis at 20 rad/s
will undergo precession when a torque 100 N-m is applied about an axis normal
to it at an angular speed, if mass moment of inertia of the disc is the 1 kg-m2
(a) 2 rad/s
(b)
5 rad/s
(c) 10 rad/s
(d) 20 rad/s
2. 18. The engine of an aeroplane rotates in
clockwise direction when seen from the tail end and the aeroplane takes a turn
to the left. The effect of the gyroscopic couple on the aeroplane will be
(a)
to raise the nose and dip the tail
(b) to dip the nose and raise the tail
(c) to raise the nose and tail
(d) to dip the nose and tail
3. 19. The air screw of an aeroplane is
rotating clockwise when looking from the front. If it makes a left turn, the
gyroscopic effect will
(a) tend to depress the nose and raise
the tail
(b)
tend to raise the nose and depress the tail
(c) tilt the aeroplane
(d) none of the above
4. 20.The rotor of a ship rotates in clockwise
direction when viewed from the stern and the ship takes a left turn. The effect
of the gyroscopic couple acting on it will be
(a) to raise the bow and stern
(b) to lower the bow and stern
(c)
to raise the bow and lower the stern
(d) to lower the bow and raise the stern
5. 21. When the pitching of a ship is upward,
the effect of gyroscopic couple acting on it will be
(a) to move the ship towards port side
(b)
to move the ship towards star-board
(c) to raise the bow and lower the stern
(d) to raise the stern and lower the bow
6. 22. In an automobile, if the vehicle makes a
left turn, the gyroscopic torque
(a)
increases the forces on the outer wheels
(b) decreases the forces on the outer
wheels
(c) does not affect the forces on the
outer wheels
(d) none of the above
7. 23. A motor car moving at a certain speed
takes a left turn in a curved path. If the engine rotates in the same direction
as that of wheels, then due to the centrifugal forces
(a) the reaction on the inner wheels
increases and on the outer wheels decreases
(b)
the reaction on the outer wheels increases and on the inner wheels decreases
(c) the reaction on the front wheels
increases and on the rear wheels decreases
(d) the reaction on the rear wheels
increases and on the front wheels decreases
24. It is required to
lift water at the top of a high building at the rate of 50 litres/min. Assuming
the losses due to friction equivalent to 5 m and those due to leakage equal to
5 m head of water, efficiency of pump 90%, decide the kilowatt capacity of
motor required to drive the pump.
a) 0.102 kW
b) 0.202 kW
c) 0.302 kW
d) 0.402 kW
25.
A power screw is
rotated at constant angular speed of 1.5 revolutions/sec by applying a steady
torque of 1.5Nm. How much work is done per revolution? What is the power
required?
a) 141.36 W
b) 241.36 W
c) 341.36 W
d) 441.36 W
26.
Power is transmitted
by an electric motor to a machine by using a belt drive. The tensions on the
tight and slack side of the belt are 2200 N and 1000 N respectively and
diameter of the pulley is 600 mm. If speed of the motor is 1500 r.p.m, find the
power transmitted.
a) 46.548 kW
b) 56.548 kW
c) 66.548 kW
d) 76.548 kW
27.
The flywheel of an
engine has a mass of 200 kg and radius of gyration equal to 1 m. The average
torque on the flywheel is 1200 Nm. Find the angular acceleration of flywheel
and the angular speed after 10 seconds starting from rest.
a) 3 rad/s
b) 4 rad/s
c) 5 rad/s
d) 6 rad/s
28.
Calculate the moment
of inertia and radius of gyration of a solid sphere of mass 10 kg and diameter
6.5m about its centroidal axis.
a) 2.055 m
b) 3.055 m
c) 4.055 m
d) 5.055 m
29.
Calculate the work
done per minute by a punch tool making 20 working strokes per min when a 30 mm
diametre hole is punched in 5 mm thick plate with ultimate shear strength og
450 Mpa in each stroke.
a) 10.69 kNm
b) 20.69 kNm
c) 30.69 kNm
d) 40.69 kNm
30.
In latitude 25.0 S,
SA (spin axis) of a FG (free gyro) is in position S40E and horizontal. Find the
tilt after 6 hours.
a) 61.16 up
b) 61.16 down
c) 51.15 up
d) none of the mentioned
31.
The steering of a
ship means
a) movement of a complete ship up and down in vertical plane about transverse
axis
b) turning of a complete ship in a
curve towards right r left, while it moves forward
c) rolling of a complete ship sideways
d) none of the mentioned
32.
When the pitching of
a ship is upward, the effect of gyroscopic couple acting on it will be
a) to move the ship towards starboard
b) to move the ship towards port side
c) to raise the bow and lower the stern
d) to raise the stern and lower the bow
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