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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)

Correct Answer :

B. tanα/tan (α +φ)


Related Questions

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4

The maximum efficiency of a screw jack is

A. (1 - sinφ)/(1 + sinφ)

B. (1 + sinφ)/(1 - sinφ)

C. (1 - tanφ)/(1 + tanφ)

D. (1 + tanφ)/(1 - tanφ)

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4

A slider crank chain consists of following numbers of turning and sliding pairs

A. 1, 3

B. 2, 2

C. 3, 1

D. 4, 0

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4

When the crank is at the outer dead centre, in a reciprocating steam engine, then the acceleration of the piston will be

A. ω² r {(n + 1)/n}

B. ω² r {(n - 1)/n}

C. ω² r {n/(n + 1)}

D. ω² r {n/(n - 1)}

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4

If ω/ωn is very high 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 direction of linear velocity of any point on a link with respect to another point on the same link is

A. Parallel to the link joining the points

B. Perpendicular to the link joining the points

C. At 45° to the link joining the points

D. None of the above

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4

The brake commonly used in railway trains is

A. Shoe brake

B. Band brake

C. Band and block brake

D. Internal expanding brake

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4

If two moving elements have surface contact in motion, such pair is known as

A. Sliding pair

B. Rolling pair

C. Surface pair

D. Higher pair

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4

The natural frequency of free transverse vibrations due to a point load acting over a simply supported shaft is equal to (where δ = Static deflection of a simply supported shaft due to the point load)

A. 0.4985/√δ

B. 0.5615/√δ

C. 0.571/√δ

D. 0.6253/√δ

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4

Pulley in a belt drive acts as

A. Cylindrical pair

B. Turning pair

C. Rolling pair

D. Sliding pair

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4

In the below figure, PC is the connecting rod and OC is the crank making an angle θ with the line of stroke PO and rotates with uniform angular velocity at ω rad/s. The Klien's acceleration diagram for determining the acceleration of the piston P is shown by quadrilateral CQNO. The acceleration of the piston P with respect to the crankpin C is given by

A. ω² × NO

B. ω² × CO

C. ω² × CN

D. ω² × QN

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4

In order to balance the reciprocating masses,

A. Primary forces and couples must be balanced

B. Secondary forces and couples must be balanced

C. Both (A) and (B)

D. None of these

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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

In a Hartnell governor, the compression of the spring is __________ the lift of the sleeve.

A. Equal to

B. Less than

C. Greater than

D. None of these

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4

A shaft has two heavy rotors mounted on it. The transverse natural frequencies, considering each of the rotor separately, are 100 Hz and 200 Hz respectively. The lowest critical speed is

A. 5,367 r.p.m.

B. 6,000 r.p.m.

C. 9,360 r.p.m.

D. 12,000 r.p.m.

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4

In a Hartnell governor, the lift of the sleeve is given by (where r₁ and r₂ = Max. and min. radii of rotation, x = Length of ball arm of the lever, and y = Length of sleeve arm of the lever)

A. (r₁ + r₂) (y/x)

B. (r₁ + r₂) (x/y)

C. (r₁ - r₂) (y/x)

D. (r₁ - r₂) (x/y)

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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

In automobiles the power is transmitted from gear box to differential through

A. Bevel gear

B. Universal joint

C. Hooke's joint

D. Knuckle joint

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4

A spring controlled governor is said to be unstable when the controlling force

A. Increases as the radius of rotation decreases

B. Increases as the radius of rotation increases

C. Decreases as the radius of rotation increases

D. Remains constant for all radii of rotation

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4

In a circular arc cam with roller follower, the acceleration in any position of the lift will depend only upon

A. Total lift, total angle of lift, minimum radius of cam and cam speed

B. Radius of circular arc, cam speed, location of centre of circular arc and roller diameter

C. Mass of cam follower linkage, spring stiffness and cam speed

D. Total lift, centre of gravity of the cam and cam speed

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4

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

A. Stable

B. Unstable

C. Isochronous

D. None of these

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4

The rotating shafts tend to vibrate violently at whirling speeds because

A. The system is unbalanced

B. Bearing centre line coincides with the axis

C. The shafts are rotating at very high speeds

D. Resonance is caused due to the heavy mass of the rotor

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4

Angle of descent 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 the 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

A machine mounted on a single coil spring has a period of free vibration of tp . If the spring is cut into four equal parts and placed in parallel and the machine is mounted on them, then the period of free vibration of the new system will become

A. tp /16

B. tp /4

C. 4 tp

D. 16 tp

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4

When a ship travels in a sea, which of the effect is more dangerous

A. Steering

B. Pitching

C. Rolling

D. All of the above

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4

The C.G. of a link in any mechanism would experience

A. No acceleration

B. Linear acceleration

C. Angular acceleration

D. Both angular and linear accelerations

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4

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

A. Twice

B. Four times

C. Eight times

D. Sixteen times

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4

The critical speed of a shaft in revolution per second is __________ as that of natural frequency of transverse vibration.

A. Same

B. Different

C. Unpredictable

D. None of these

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4

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

A. 1.4 N-s/m

B. 18.52 N-s/m

C. 52.92 N-s/m

D. 529.2 N-s/m

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4

The magnitude of linear velocity of a point B on a link AB relative to point A is (Where ω = Angular velocity of the link AB)

A. ω × AB

B. ω × (AB)²

C. ω² × AB

D. (ω × AB)²

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4

Which of the following statement is wrong?

A. The difference between the maximum and minimum energies is called maximum fluctuation of energy

B. The coefficient 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 above