In a cam drive with uniform velocity follower, the sharp corners of the displacement diagram are rounded off at the beginning and at the end of each stroke. This is done
Because of difficulty in manufacturing cam profile
Because of loose contact of follower with cam surface
In order to have acceleration in beginning and retardation at the end of stroke within the finite limits
Because the uniform velocity motion is a partial parabolic motion
Correct Answer :
C. In order to have acceleration in beginning and retardation at the end of stroke within the finite limits
Related Questions
A spring controlled governor is found unstable. It can be made stable by
Increasing the spring stiffness
Decreasing the spring stiffness
Increasing the ball mass
Decreasing the ball mass
Two pulleys of radii r₁ and r₂ and at distance x apart are connected by means of an open belt drive. The length of the belt is
π (r₁ + r₂) + (r₁ + r₂)²/x + 2x
π (r₁ + r₂) + (r₁ - r₂)²/x + 2x
π (r₁ - r₂) + (r₁ - r₂)²/x + 2x
π (r₁ - r₂) + (r₁ + r₂)²/x + 2x
Longitudinal vibrations are said to occur when the particles of a body moves
Perpendicular to its axis
Parallel to its axis
In a circle about its axis
None of these
The critical speed of a shaft with a disc supported in between is equal to the natural frequency of the system in
Transverse vibrations
Torsional vibrations
Longitudinal vibrations
All of these
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?
All points of the disc have the same velocity
The centre of the disc has zero acceleration
The centre of the disc has centrifugal acceleration
The point on the disc making contact with the plane surface has zero acceleration
Higher pairs are those which have
Point or line contact between the two elements when in motion
Surface contact between the two elements when in motion
Elements of pairs not held together mechanically
Two elements that permit relative motion
In a reciprocating steam engine, when the crank has turned from inner dead centre through an angle θ, the angular velocity of the connecting rod is given by
ω sinθ/(n² - sin²θ)1/2
ω cosθ/(n² - cos²θ)1/2
ω sinθ/(n² - cos²θ)1/2
ω cosθ/(n² - sin²θ)1/2
The primary unbalanced force due to inertia of reciprocating parts in a reciprocating engine is given by (where m = Mass of reciprocating parts, ω = Angular speed of crank, r = Radius of crank, θ = Angle of inclination of crank with the line of stroke, and n = Ratio of the length of connecting rod to radius of crank)
m.ω².r sinθ
m.ω².r cosθ
m.ω².r (sin 2θ/n)
m.ω².r (cos 2θ/n)
In a four stroke I.C. engine, the turning moment during the compression stroke is
Positive throughout
Negative throughout
Positive during major portion of the stroke
Negative during major portion of the stroke
Which of the following mechanisms produces mathematically an exact straight line motion?
Grasshopper mechanism
Watt mechanism
Peaucellier's mechanism
Tchebicheff mechanism
In a simple train of wheels, the velocity ratio __________ the intermediate wheels.
Depends upon
Is independent of
Either A or B
None of these
There are six gears A, B, C, D, E and F in a compound train. The numbers of teeth in the gears are 20, 60, 30, 80, 25 and 75 respectively. The ratio of angular speeds of the driven (F) to the driver (A) of the drive is
1/24
1/8
4/15
12
Peaucelliers mechanism has
Eight links
Six links
Four links
Twelve links
The partial balancing means
Balancing partially revolving masses
Balancing partially reciprocating masses
Best balancing of engines
All of these
In a steam engine, the earlier cut-off with a simple slide valve may be obtained by increasing the steam lap and the angle of advance of the eccentric but keeping constant the travel and lead of the valve, this method will
Cause withdrawing or throttling of steam
Reduce length of effective stroke of piston
Reduce maximum opening of port to steam
All of these
If D₁ and D₂ be the diameters of driver and driven pulleys, then belt speed is proportional to
D₁/D₂
D₂/D₁
D₁.D₂
D₁
The frictional torque transmitted in a flat pivot bearing, assuming uniform wear, is (Where μ = Coefficient of friction, W=Load over the bearing, R=Radius of bearing)
μwr
¾μWR
(2/3) μWR
½μWR
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
Which of the following is a higher pair?
Belt and pulley
Turning pair
Screw pair
Sliding pair
When a point moves along a straight line, its acceleration will have
Radial component only
Tangential component only
Coriolis component only
Radial and tangential components both
In a gear having involute teeth, the normal to the involute is a tangent to the
Pitch circle
Base circle
Addendum circle
Dedendum circle
Which is the false statement about the properties of instantaneous centre?
At the instantaneous center of rotation, one rigid link rotates instantaneously relative to another for the configuration of mechanism considered
The two rigid links have no linear velocities relative to each other at the instantaneous centre
The two rigid links which have no linear velocity relative to each other at this center have the same linear velocity to the third rigid link
The double centre can be denoted either by O2 or O12, but proper selection should be made
The C.G. of a link in any mechanism would experience
No acceleration
Linear acceleration
Angular acceleration
Both angular and linear accelerations
In a reciprocating steam engine, which of the following forms a kinematic link?
Cylinder and piston
Piston rod and connecting rod
Crankshaft and flywheel
Flywheel and engine frame
The direction of Coriolis component of acceleration is the direction
Of relative velocity vector for the two coincident points rotated by 90° in the direction of the angular velocity of the rotation of the link
Along the centripetal acceleration
Along tangential acceleration
Along perpendicular to angular velocity
The advantage of the piston valve over the slide valve is that in the former case
Wear is less
Power absorbed is less
Both wear and power absorbed are low
The pressure developed being high provides tight sealing
Typewriter constitutes
Machine
Structure
Mechanism
Inversion
Kinematic pairs are those which have two elements that
Have line contact
Have surface contact
Permit relative motion
Are held together
In a reciprocating engine, usually __________ of the reciprocating masses are balanced.
One-half
Two-third
Three-fourth
Whole
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
Turning pair
Rolling pair
Sliding pair
Spherical pair