4

# 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

D. The double centre can be denoted either by O2 or O12, but proper selection should be made

4

ω √(x² - r²)

ω √(r² - x²)

ω² √(x² - r²)

ω² √(r² - x²)

4

# The rotating shafts tend to vibrate violently at whirling speeds because

The system is unbalanced

Bearing centre line coincides with the axis

The shafts are rotating at very high speeds

Resonance is caused due to the heavy mass of the rotor

4

# Which type of gearing is used in steering system of an automobile?

Rack and pinion

Worm and wheel

Spiral gears

None of the above

4

Equal to

Less than

Greater than

None of these

4

Minimum

Maximum

Zero

Infinity

4

Lower pair

Higher pair

Spherical pair

Cylindrical pair

4

# Which of the following disciplines provides study of the relative motion between the parts of a machine and the forces acting on the parts?

Theory of machines

Applied mechanics

Mechanisms

Kinetics

4

Screw pair

Spherical pair

Turning pair

Sliding pair

4

4

# The velocity of piston in a reciprocating steam engine is given by (where ω = Angular velocity of crank, r = Radius of crank pin circle, θ = Angle turned by crank from inner dead centre, and n = Ratio of length of connecting rod to the radius of crank)

ωr [sin θ + (sin 2θ/n)]

ωr [cos θ + (cos 2θ/n)]

ω²r [sin θ + (sin 2θ/n)]

ω²r [cos θ + (cos 2θ/n)]

4

1, 3

2, 2

3, 1

4, 0

4

Structure

Mechanism

Kinematic chain

Inversion

4

# In order to balance the reciprocating masses,

Primary forces and couples must be balanced

Secondary forces and couples must be balanced

Both (A) and (B)

None of these

4

# The maximum efficiency of spiral gears is (where θ = Shaft angle, and φ = Friction angle)

sin (θ + φ) + 1/ cos (θ - φ) + 1

cos (θ - φ) + 1/ sin (θ + φ) + 1

cos (θ + φ) + 1/ cos (θ - φ) + 1

cos (θ - φ) + 1/ cos (θ + φ) + 1

4

Small

Too small

Large

Too large

4

# 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

4

# Creep in belt drive is due to

Material of the pulley

Material of the belt

Larger size of the driver pulley

Uneven extensions and contractions due to varying tension

4

# The working depth of a gear is the radial distance from the

Pitch circle to the bottom of a tooth

Pitch circle to the top of a tooth

Top of a tooth to the bottom of a tooth

Addendum circle to the clearance circle

4

Two forks

One fork

Three forks

Four forks

4

# The centre distance between two meshing involute gears is equal to

Difference of base circle radii/ cosφ

Sum of pitch circle radii/ cosφ

Difference of pitch circle radii/ cosφ

4

# Which of the following statement is correct?

The primary unbalanced force is less than the secondary unbalanced force.

The primary unbalanced force is maximum twice in one revolution of the crank.

The unbalanced force due to reciprocating masses varies in magnitude and direction both.

The magnitude of swaying couple in locomotives is inversely proportional to the distance between the two cylinder centre lines

4

Closed pair

Open pair

Mechanical pair

Rolling pair

4

0

1

2

-1

4

# In gears, interference takes place when

The tip of a tooth of a mating gear digs into the portion between base and root circles

Gears do not move smoothly in the absence of lubrication

Pitch of the gears is not same

Gear teeth are undercut

4

Ellipse

Circle

Parabola

Hyperbola

4

# Kinematic 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

4

# In a steam engine, one method of obtaining the earlier cut-off with a simple slide valve is by increasing the angle of advance of the eccentric while the throw of the eccentric, steam lap and exhaust lap are kept constant. 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

4

# The maximum or minimum value of the swaying couple is

± c.m.ω².r

± a (1 - c) m.ω².r

± (a/√2) (1 - c) m.ω².r

± 2a (1 - c) m.ω².r

4

# The size of a gear is usually specified by

Pressure angle

Circular pitch

Diametral pitch

Pitch circle diameter