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Current Affairs January 2024

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4

Whirling speed of the shaft is the speed at which

A. Shaft tends to vibrate in longitudinal direction

B. Torsional vibrations occur

C. Shaft tends to vibrate vigorously in transverse direction

D. Combination of transverse and longitudinal vibration occurs

Correct Answer :

C. Shaft tends to vibrate vigorously in transverse direction


Related Questions

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4

The contact ratio is given by

A. (Length of the path of approach)/(Circular pitch)

B. (Length of path of recess)/(Circular pitch)

C. (Length of the arc of contact)/(Circular pitch)

D. (Length of the arc of approach)/cosφ

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4

The frequency of oscillation of a torsional pendulum is

A. 2πk/r. √(g/l)

B. r/2πk. √(l/g)

C. 2πr/k. √(g/l)

D. r/2πk. √(g/l)

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4

If ω/ωn is very low for a body vibrating under steady state vibrations, the phase angle for all values of damping factors, will tend to approach

A.

B. 90°

C. 180°

D. 360°

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4

The Kutzbach criterion for determining the number of degrees of freedom (n) is (where l = number of links, j = number of joints and h = number of higher pairs)

A. n = 3(l - 1) - 2j - h

B. n = 2(l - 1) -2j - h

C. n = 3(l - 1) - 3j - h

D. n = 2(l - 1) - 3j - h

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4

Efficiency of a screw jack is given by

A. tan (α + φ)/tanα

B. tanα/tan (α +φ)

C. tan (α - φ)/tanα

D. tanα/tan (α - φ)

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4

The coriolis component of acceleration is taken into account for

A. Slider crank mechanism

B. Four bar chain mechanism

C. Quick return motion mechanism

D. All of these

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4

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

D. Under damped vibration

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4

When the primary direct crank of a reciprocating engine makes an angle of 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.

D.

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4

The two elements of a pair are said to form a _________ when they permit relative motion between them.

A. Open pair

B. Kinematic pair

C. Sliding pair

D. None of these

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4

The method of direct and reverse cranks is used in engines for

A. The control of speed fluctuations

B. Balancing of forces and couples

C. Kinematic analysis

D. Vibration analysis

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4

The partial balancing of reciprocating parts in locomotives produces

A. Hammer blow

B. Swaying couple

C. Variation in tractive force along the line of stroke

D. All of the above

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4

The velocity of the reciprocating roller follower when it has contact with the straight flanks of the tangent cam, is given by (where ω = Angular velocity of the cam shaft)

A. ω (r₁ r₂) sinθ

B. ω (r₁ + r₂) sinθ sec2θ

C. ω (r₁ r₂) cosθ

D. ω (r₁ + r₂) cosθ cosec2θ

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4

The frictional torque transmitted in a flat collar bearing, considering uniform wear, is (where r₁ and r₂ = External and internal radii of collar respectively)

A. (1/2) μ W (r₁ + r₂)

B. (2/3) μ W (r₁ + r₂)

C. (1/2) μ W [(r₁³ - r₂³)/(r₁² - r₂²)]

D. (2/3) μ W [(r₁³ - r₂³)/(r₁² - r₂²)]

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4

A body is said to be under forced vibrations, when

A. There is a reduction in amplitude after every cycle of vibration

B. No external force acts on a body, after giving it an initial displacement

C. A body vibrates under the influence of external force

D. None of the above

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4

Angle of ascent of cam is defined as the angle

A. During which the follower returns to its initial position

B. Of rotation of the cam for a definite displacement of the follower

C. Through which the cam rotates during the period in which the follower remains in highest position

D. Moved by the cam from the instant the follower begins to rise, till it reaches its highest position

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4

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)

A. m.ω².r sinθ

B. m.ω².r cosθ

C. m.ω².r (sin 2θ/n)

D. m.ω².r (cos 2θ/n)

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4

When the particles of a body moves perpendicular to its axis, then the body is said to have

A. Longitudinal vibration

B. Transverse vibration

C. Torsional vibration

D. None of these

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4

The equation of motion for a single degree of freedom system with viscous damping is 4(dx²/dt²) + 9(dx/dt) + 16x. The damping ratio of the system is

A. 9/8

B. 9/82

C. 9/16

D. 9/128

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4

In a multiple V-belt drive, when a single belt is damaged, it is preferable to change the complete set to

A. Reduce vibration

B. Reduce slip

C. Ensure uniform loading

D. Ensure proper alignment

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4

Pitch point on a cam is

A. Any point on pitch curve

B. The point on cam pitch curve having the maximum pressure angle

C. Any point on pitch circle

D. The point on cam pitch curve having the minimum pressure angle

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4

In a Hartnell governor, the stiffness of the spring is given by (where S1 and S2 = Spring forces exerted on the sleeve at max. and min. radii of rotation, and h = Compression of the spring)

A. (S₁ + S₂)/h

B. (S₁ - S₂)/h

C. (S₁ + S₂)/2h

D. (S₁ - S₂)/2h

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4

The periodic time of a compound pendulum is __________ when the distance between the point of suspension and the centre of gravity is equal to the radius of gyration of the body about its centre of gravity.

A. Zero

B. Minimum

C. Maximum

D. None of these

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4

The lead screw of a lathe with nut forms a

A. Rolling pair

B. Sliding pair

C. Screw pair

D. Turning pair

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4

The ratio of height of Porter governor (when length of arms and links are equal) to the height of Watt's governor is (where m = Mass of the ball, and M = Mass on the sleeve)

A. m/(m + M)

B. M/(m + M)

C. (m + M)/m

D. (m + M)/M

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4

Which of the following is a turning pair?

A. Piston and cylinder of a reciprocating steam engine

B. Shaft with collars at both ends fitted into a circular hole

C. Lead screw of a lathe with nut

D. Ball and a socket joint

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4

When the nature of contact between the elements of a pair is such that one element can turn about the other by screw threads, the pair is known as a

A. Screw pair

B. Spherical pair

C. Turning pair

D. Sliding pair

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4

A chain comprises of 5 links having 5 joints. Is it kinematic chain?

A. Yes

B. No

C. It is a marginal case

D. Data are insufficient to determine it

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4

If the radius of gyration of a compound pendulum about an axis through e.g. is more, then its frequency of oscillation will be

A. Less

B. More

C. Same

D. Data are insufficient to determine same

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4

The static balancing is satisfactory for low speed rotors but with increasing speeds, dynamic balancing becomes necessary. This is because, the

A. Unbalanced couples are caused only at higher speeds

B. Unbalanced forces are not dangerous at higher speeds

C. Effects of unbalances are proportional to the square of the speed

D. Effects of unbalances are directly proportional to the speed

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4

The natural frequency of free transverse vibrations due to uniformly distributed load acting over a simply supported shaft is (where δS = Static deflection of simply supported shaft due to uniformly distributed load)

A. 0.4985/ √δS

B. 0.5615/ √δS

C. 0.571/ √δS

D. 0.6253/ √δS