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Theory of machines
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Science
Class 8
Solar System
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Theory of machines
mcqs by everyone
The coriolis component of acceleration acts
at 45° to the sliding surface
perpendicular to the sliding surface
along the sliding surface
parallel to the sliding surface
Scotch yoke mechanism is used to generate
sine functions
inversions
square roots
logarithms
An involute pinion and gear are inmesh.
If both have the same size of addendum, then there will be an interference between the
flanks of both gear and pinion
tip of both gear and pinion
tip of the pinion and flank of gear
tip of the gear tooth and flank of pinion
In full depth involute system, the smallest number of teeth in a pinion which meshes with rack without interference is
32
12
16
25
When the load on the engine increases, it becomes necessary to increase the supply of working fluid and when the load decreases, less working fluid isrequired.
The supply of the working fluid to the engine is controlled by a
D-slide valve
Governor
flywheel
Meyer's expansion valve
A mass of 1 kg is attached to the end of a spring with a stiffness of 0.7 N/mm. The critical damping coefficient of this system is
52.92 N-s/m
529.2 N-s/m
18.52 N-s/m
1.4 N-s/m
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 clockwise direction, then the rubbing velocity at the pin joint O is (where r = Radius of the pin at O)
( ω1 + ω2)r
( ω1 - ω2)r
ω1.ω2.r
( ω1 - ω2)2r
A system in dynamic balance implies that
there will absolutely no wear of bearings
the system is critically damped
there is no critical speed in the system
the system is also statically balanced
When the crank is at the inner dead centre, in a reciprocating steam engine, then the velocity of the piston will be
Zero
Minimum
NONE OF THESE
maximum
Effort of a governor is the
workdone at the sleeve for maximum equilibrium speed
None of the above
mean force exerted at the sleeve for maximum equilibrium speed
mean force exerted at the sleeve for a given percentage change of speed
In vibration isolation system, the transmissibility will be equal to unity, for all values of damping factor, if ω/ωn is
equal to 2
less than 2
greater than 2
equal to one
In a single slider crank chain
one is a turning pair and three are sliding pairs
two are turning pairs and two are sliding pairs
each of the four pairs is a turning pair
three are turning pairs and one is a sliding pair
The factional torque for square thread at the mean radius r while raising load W is given by
T = W.r tan(φ + α)
T = W.r tan(φ - α)
T = W.r tan φ
T = W.r tan α
In involute gears, the pressure angle is
dependent on the size of gears
always variable
always constant
dependent on the size of teeth
The static balancing is satisfactory for low speed rotors but with increasing speeds, dynamic balancing becomesnecessary.
This is because, the
unbalanced couples are caused only at higher speeds
unbalanced forces are not dangerous at higher speeds
effects of unbalances are directly proportional to the speed
effects of unbalances are proportional to the square of the speed
The acceleration of a particle at any instant has two components
i.e. radial component and tangentialcomponent.
These two components will be
opposite to each other
inclined at 45°
parallel to each other
perpendicular to each other
The method of obtaining different mechanisms by fixing in turn different links in a kinematic chain, is known as
compound mechanism
inversion
Machine
structure
When the relation between the controlling force (Fc) and radius of rotation (r) for a spring controlled governor is Fc = ar + b, then the governor will be
Unstable
NONE OF THESE
isochronous
Stable
An exact straight line motion mechanism is a
Scott-Russell's mechanism
Peaucellier's mechanism
All of These
Hart's mechanism
A combination of kinematic pairs, joined in such a way that the relative motion between the links is completely constrained, is called a
mechanism
structure
kinematic chain
inversion
A shaft has two heavy rotors mounted on it. The transverse natural frequencies, considering each of the rotor separately, are 100 Hz and 200 Hzrespectively.
The lowest critical speed is
9360 r.p.m.
12000 r.p.m.
6000 r.p.m.
5367 r.p.m.
The mechanism consisting of three turning pairs and one sliding pair, is called a
All of the above
crank and slotted lever quick return motion mechanism
single slider crank chain
Whitworth quick return motion mechanism
The working depth of a gear is the radial distance from the
addendum circle to the clearance circle
pitch circle to the bottom of a tooth
top of a tooth to the bottom of a tooth
pitch circle to the top of a tooth
Bifilar suspension method is used to find the
frequency of vibration of the body
periodic time of the body
moment of inertia of the body
angular acceleration of the body
The instantaneous centre of a rigid thin disc rolling on a plane rigid surface is located at
the point of contact
the point on the circumference situated vertically opposite to the contact point
an infinite distance on the plane surface
the centre of the disc
The coriolis component of acceleration depends upon
Both (a) and (b)
NONE OF THESE
velocity of slider
angular velocity of the link
The two parallel and coplaner shafts are connected by gears having teeth parallel to the axis of theshaft.
This arrangement is known as
spur gearing
spiral gearing
bevel gearing
helical gearing
A reed type tachometer use the principle of
damped free vibration
transverse vibration
longitudinal vibration
torsional vibration
When the speed of the engine fluctuates continuously above and below the mean speed, the governor is said to be
isochronous
Unstable
hunt
Stable
A motor car moving at a certain speed takes a left turn in a curvedpath.
If the engine rotates in the same direction as that of wheels, men due to centrifugal force
the reaction on the outer wheels increases and on the inner wheels decreases
the reaction on me inner wheels increases and on the outer wheels decreases
the reaction on the rear wheels increases and on the front wheels decreases
the reaction on the front wheels increases and on the rear wheels decreases
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