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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

Correct Answer :

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


Related Questions

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4

The loss of kinetic energy during inelastic impact, is given by (where m1 = Mass of the first body, m2 = Mass of the second body, and u1 and u2 = Velocities of the first and second bodies respectively.)

A. [m₁ m₂/2(m₁ + m₂)] (u₁ - u₂)²

B. [2(m₁ + m₂)/m₁ m₂] (u₁ - u₂)²

C. [m₁ m₂/2(m₁ + m₂)] (u₁² - u₂²)

D. [2(m₁ + m₂)/m₁ m₂] (u₁² - u₂²)

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4

A redundant frame is also called __________ frame.

A. Perfect

B. Imperfect

C. Deficient

D. None of these

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4

According to principle of moments

A. If a system of coplanar forces is in equilibrium, then their algebraic sum is zero

B. If a system of coplanar forces is in equilibrium, then the algebraic sum of their moments about any point in their plane is zero

C. The algebraic sum of the moments of any two forces about any point is equal to moment of the resultant about the same point

D. Positive and negative couples can be balanced

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4

The unit of angular acceleration is

A. N-m

B. m/s

C. m/s2

D. rad/s2

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4

The static friction

A. Bears a constant ratio to the normal reaction between the two surfaces

B. Is independent of the area of contact, between the two surfaces

C. Always acts in a direction, opposite to that in which the body tends to move

D. All of the above

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4

A sample of metal weighs 219 gms in air, 180 gms in water, 120 gms in an unknown fluid. Then which is correct statement about density of metal

A. Density of metal can't be determined

B. Metal is twice as dense as water

C. Metal will float in water

D. Metal is twice as dense as unknown fluid

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4

If a body is acted upon by a number of coplanar non-concurrent forces, it may

A. Rotate about itself without moving

B. Move in any one direction rotating about itself

C. Be completely at rest

D. All of these

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4

If a suspended body is struck at the centre of percussion, then the pressure on die axis passing through the point of suspension will be

A. Maximum

B. Minimum

C. Zero

D. Infinity

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4

D' Alembert's principle is used for

A. Reducing the problem of kinetics to equivalent statics problem

B. Determining stresses in the truss

C. Stability of floating bodies

D. Designing safe structures

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4

The velocity ratio of a differential wheel and axle with D as the diameter of effort wheel and d1 and d2 as the diameters of larger and smaller axles respectively, is

A. D/(d₁ + d₂)

B. D/(d₁ - d₂)

C. 2D/(d₁ + d₂)

D. 2D/(d₁ - d₂)

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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

A body moves, from rest with a constant acceleration of 5 m per sec. The distance covered in 5 sec is most nearly

A. 38 m

B. 62.5 m

C. 96 m

D. 124 m

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4

If the body falls freely under gravity, then the gravitational acceleration is taken as

A. +8.9 m/s2

B. -8.9 m/s2

C. +9.8 m/s2

D. -9.8 m/s2

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4

Limiting force of friction is the

A. Tangent of angle between normal reaction and the resultant of normal reaction and limiting friction

B. Ratio of limiting friction and normal reaction

C. The friction force acting when the body is just about to move

D. The friction force acting when the body is in motion

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4

A lead ball with a certain velocity is made to strike a wall, it falls down, but rubber ball of same mass and with same velocity strikes the same wall, it rebounds. Select the correct reason from the following:

A. Both the balls undergo an equal change in momentum

B. The change in momentum suffered by rubber ball is more than the lead ball

C. The change in momentum suffered by rubber ball is less than the lead ball

D. None of the above

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4

Three forces acting on a rigid body are represented in magnitude, direction and line of action by the three sides of a triangle taken in order. The forces are equivalent to a couple whose moment is equal to

A. Area of the triangle

B. Twice the area of the triangle

C. Half the area of the triangle

D. None of these

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4

Which one of the following statements is not correct?

A. The tangent of the angle of friction is equal to coefficient of friction

B. The angle of repose is equal to angle of friction

C. The tangent of the angle of repose is equal to coefficient of friction

D. The sine of the angle of repose is equal to coefficient to friction

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4

The velocity ratio of a differential pulley block with D and d as the diameters of larger and smaller pulley, is

A. D/(D - d)

B. D/(D + d)

C. 2D/(D - d)

D. 2D/(D + d)

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4

Moment of inertia of a hollow rectangular section as shown in the below figure about X-X axis, is

A. (BD³/12) - (bd³/12)

B. (DB³/12) - (db³/12)

C. (BD³/36) - (bd³/36)

D. (DB³/36) - (db³/36)

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4

Moment of inertia of a triangular section of base (b) and height (h) about an axis through its base, is

A. bh3/4

B. bh3/8

C. bh3/12

D. bh3/36

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4

A framed structure, as shown in the below figure, is a

A. Perfect frame

B. Deficient frame

C. Redundant frame

D. None of the above

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4

The centre of gravity of a trapezium with parallel sides a and b lies at a distance of y from the base b, as shown in the below figure. The value of y is

A. h [(2a + b)/(a + b)]

B. (h/2) [(2a + b)/(a + b)]

C. (h/3) [(2a + b)/(a + b)]

D. (h/3) [(a + b)/(2a + b)]

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4

Which of the following is not the unit of energy?

A. kg m

B. kcal

C. Watt

D. Watt hours

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4

In order to completely specify angular displacement by a vector, it must fix

A. Direction of the axis of rotation

B. Magnitude of angular displacement

C. Sense of angular displacement

D. All of these

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4

In the shown figure, if the angle of inclination of the plane is increased, then acceleration of the system will

A. Increase

B. Decrease

C. Remain the same

D. None of these

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4

In a framed structure, as shown in the below figure, the forces in the members AB and BC are respectively

A. √3. W (tensile) and 2W (compressive)

B. 2W (tensile) and √3. W (compressive)

C. 2√3. W (tensile) and 2√3. W (compressive)

D. None of the above

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4

The C.G. of a right circular solid cone of height h lies at the following distance from the base

A. h/2

B. J/3

C. h/6

D. h/4

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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

For any system of coplanar forces, the condition of equilibrium is that the

A. Algebraic sum of the horizontal components of all the forces should be zero

B. Algebraic sum of the vertical components of all the forces should be zero

C. Algebraic sum of moments of all the forces about any point should be zero

D. All of the above

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4

The frequency of oscillation of a compound pendulum is (where kG = Radius of gyration about the centroidal axis, and h = Distance between the point of suspension and C.G. of the body.)

A. 2π. √(gh/kG² + h²)

B. 2π. √(kG² + h²/gh)

C. 1/2π. √(gh/kG² + h²)

D. 1/2π. √(kG² + h²/gh)