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Current Affairs January 2024

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4

Efficiency of a screw jack is given by (where α = Helix angle, and φ = Angle of friction.)

A. tan(α + φ)/tanα

B. tanα/tan (α + φ)

C. tan(α - φ)/tanα

D. None of these

Correct Answer :

B. tanα/tan (α + φ)


Related Questions

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4

The angle of inclination of the plane at which the body begins to move down the plane, is called

A. Angle of friction

B. Angle of repose

C. Angle of projection

D. None of these

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4

A block of mass m1, placed on an inclined smooth plane is connected by a light string passing over a smooth pulley to mass m2, which moves vertically downwards as shown in the below figure. The tension in the string is

A. m1/m2

B. m1. g. sin α

C. m1.m2/m1 + m2

D. m1. m2.g (1 + sin α)/(m1 + m2)

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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

One joule is equal to

A. 0.1 N-m

B. 1 N-m

C. 10 N-m

D. 100 N-m

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4

If u1 and u2 are the velocities of two moving bodies in the same direction before impact and v1 and v2 are their velocities after impact, then coefficient of restitution is given by

A. (v1 - v2)/(u1 - u2)

B. (v₂ - v₁)/(u1 - u2)

C. (u1 - u2)/(v1 - v2)

D. (u₂ + u₁)/(v₂ + v₁)

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4

Which of the following is not a scalar quantity?

A. Mass

B. Volume

C. Density

D. Acceleration

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4

The unit of power in S.I. units is

A. Horsepower

B. Joule

C. Watt

D. kg-m

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4

The skidding away of the vehicle on a level circular path can be avoided if the force of friction between the wheels and the ground is __________ the centrifugal force.

A. Less than

B. Greater than

C. Equal to

D. None of these

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4

If a number of forces act simultaneously on a particle, it is possible

A. Not a replace them by a single force

B. To replace them by a single force

C. To replace them by a single force through C.G.

D. To replace them by a couple

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4

Effect of a force on a body depends upon

A. Magnitude

B. Direction

C. Position or line of action

D. All of the above

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4

The M.I. of hollow circular section about a central axis perpendicular to section as compared to its M.I. about horizontal axis is

A. Same

B. Double

C. Half

D. Four times

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4

Coplanar concurrent forces are those forces which

A. Meet at one point, but their lines of action do not lie on the same plane

B. Do not meet at one point and their lines of action do not lie on the same plane

C. Meet at one point and their lines of action also lie on the same plane

D. Do not meet at one point, but their lines of action lie on the same plane

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4

The moment of inertia of a solid cylinder of mass m, radius r and length l about the longitudinal axis or polar axis is

A. mr2/2

B. mr2/4

C. mr2/6

D. mr2/8

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4

The power developed by a body acted upon by a torque T Newton metre (N - m) and revolving at ω radian/s is given by

A. T.ω (in watts)

B. T.ω/60 (in watts)

C. T.ω/75 (in kilowatts)

D. T.ω/4500 (in kilowatts)

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4

Least force required to draw a body up the inclined plane is W sin (plane inclination + friction angle) applied in the direction

A. Along the plane

B. Horizontally

C. Vertically

D. At an angle equal to the angle of friction to the inclined plane

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4

Non-coplanar non-concurrent forces are those forces which

A. Meet at one point, but their lines of action do not lie on the same plane

B. Do not meet at one point and their lines of action do not lie on the same plane

C. Do not meet at one point but their lines of action lie on the same plane

D. None of the above

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4

Mass moment of inertia of a uniform thin rod of mass M and length (l) about its mid-point and perpendicular to its length is

A. (2/3) Ml2

B. (1/3) Ml2

C. (3/4) Ml2

D. (1/12) Ml2

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4

Which of the following are vector quantities?

A. Linear displacement

B. Linear velocity

C. Linear acceleration

D. All of these

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4

The acceleration of a particle moving with simple harmonic motion, at any instant is given by

A. ω.y

B. ω2.y

C. ω2/y

D. ω3.y

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4

The total momentum of a system of masses (i. e. moving bodies) in any one direction remains constant, unless acted upon by an external force in that direction. This statement is called

A. Newton's first law of motion

B. Newton's second law of motion

C. Principle of conservation of energy

D. Principle of conservation of momentum

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4

Moment of inertia of a rectangular section having width (b) and depth (d) about an axis passing through its C.G. and parallel to the depth (d), is

A. db3/12

B. bd³/12

C. db³/36

D. bd³/36

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4

If the gravitational acceleration at any place is doubled, then the weight of a body will be

A. g/2

B. g

C. √2.g

D. 2g

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4

The unit of angular velocity is

A. m/min

B. rad/s

C. Revolutions/min

D. Both (B) and (C)

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4

The possible loading in various members of framed structures are

A. Compression or tension

B. Buckling or shear

C. Shear or tension

D. All of the above

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4

According to Lamis theorem

A. The three forces must be equal

B. The three forces must be at 120° to each other

C. The three forces must be in equilibrium

D. If the three forces acting at a point are in equilibrium, then each force is proportional to the sine of the angle between the other two

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4

According to parallel axis theorem, the moment of inertia of a section about an axis parallel to the axis through centre of gravity (i.e. IP) is given by(where, A = Area of the section, IG = Moment of inertia of the section about an axis passing through its C.G., and h = Distance between C.G. and the parallel axis.)

A. IP = IG + Ah2

B. IP = IG - Ah2

C. IP = IG / Ah2

D. IP = Ah2 / IG

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4

Which of the following is not the unit of distance?

A. Angstrom

B. Light year

C. Micron

D. Milestone

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4

The rate of change of momentum is directly proportional to the impressed force, and takes place in the same direction in which the force acts. This statement is known as

A. Newton's first law of motion

B. Newton's second law of motion

C. Newton's third law of motion

D. None of these

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4

Which of the following statement is incorrect?

A. A force acting in the opposite direction to the motion of the body is called force of friction

B. The ratio of the limiting friction to the normal reaction is called coefficient of friction

C. A machine whose efficiency is 100% is known as an ideal machine

D. The velocity ratio of a machine is the ratio of load lifted to the effort applied

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4

According to the law of moments, if a number of coplanar forces acting on a particle are in equilibrium, then

A. Their algebraic sum is zero

B. Their lines of action are at equal distances

C. The algebraic sum of their moments about any point in their plane is zero

D. The algebraic sum of their moments about any point is equal to the moment of their resultant force about the same point.