A machine having an efficiency less than 50%, is known as
Reversible machine
Non-reversible machine
Neither reversible nor non-reversible machine
Ideal machine
Correct Answer :
B. Non-reversible machine
Related Questions
The moment of a force
Is the turning effect produced by a force, on the body, on which it acts
Is equal to the product of force acting on the body and the perpendicular distance of a point and the line of action of the force
Is equal to twice the area of the triangle, whose base is the line representing the force and whose vertex is the point, about which the moment is taken
All of the above
The unit of force in S.I. system of units is
Dyne
Kilogram
Newton
Watt
During elastic impact, the relative velocity of the two bodies after impact is __________ the relative velocity of the two bodies before impact.
Equal to
Equal and opposite to
Less than
Greater than
Efficiency of a screw jack is given by (where α = Helix angle, and φ = Angle of friction.)
tan(α + φ)/tanα
tanα/tan (α + φ)
tan(α - φ)/tanα
None of these
Static friction is always __________ dynamic friction.
Equal to
Less than
Greater than
None of these
Which of the following is an equation of linear motion? (where, u and v = Initial and final velocity of the body, a = Acceleration of the body, and s = Displacement of the body in time t seconds.)
v = u + a.t
s = u.t + ½ a.t2
v2 = u2 + 2a.s
All of these
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
Newton's first law of motion
Newton's second law of motion
Principle of conservation of energy
Principle of conservation of momentum
Which of the following statement is incorrect?
A force acting in the opposite direction to the motion of the body is called force of friction
The ratio of the limiting friction to the normal reaction is called coefficient of friction
A machine whose efficiency is 100% is known as an ideal machine
The velocity ratio of a machine is the ratio of load lifted to the effort applied
The ratio of limiting friction and normal reaction is known as
Coefficient of friction
Angle of friction
Angle of repose
Sliding friction
The total motion possessed by a body, is called
Impulsive force
Mass
Weight
Momentum
For a self locking machine, the efficiency must be
Equal to 50 %
Less than 50 %
Greater than 50 %
100 %
The velocity of a body on reaching the ground from a height h, is
2.√(gh)
√(gh)
√(2gh)
2g.√h
If n = number of members and y = number of joints, then for a perfect frame, n = ?
1/2
2/3
3/2
2/4
Moment of inertia is the
Second moment of force
Second moment of area
Second moment of mass
All of these
The moment of inertia of a solid sphere of mass m and radius r is
2mr2/3
2mr2/5
mr2
mr2/2
Which of the following is not the unit of power?
kW (kilowatt)
hp (horse power)
kcal/sec
kcal/kg sec
When a body of mass m attains a velocity v from rest in time t, then the kinetic energy of translation is
mv2
mgv2
0.5 mv2
0.5 mgv2
In actual machines, mechanical advantage is __________ velocity ratio.
Equal to
Less than
Greater than
None of these
The coefficient of friction depends upon
Nature of surfaces
Area of contact
Shape of the surfaces
All of the above
The unit of work in S.I. units is
Newton
erg
kg-m
joule
The moment of inertia of a rectangular section 3 cm wide and 4 cm deep about X-X axis is
9 cm4
12 cm4
16 cm4
20 cm4
The forces, which meet at one point, but their lines of action do not lie in a plane, are called
Coplanar non-concurrent forces
Non-coplanar concurrent forces
Non-coplanar non-concurrent forces
Intersecting forces
The forces, which meet at one point and their lines of action also lie on the same plane, are known as
Coplanar concurrent forces
Coplanar non-concurrent forces
Non-coplanar concurrent forces
Non-coplanar non-concurrent forces
The potential energy of a vertically raised body is __________ the kinetic energy of a vertically falling body.
Equal to
Less than
Greater than
None of these
Coplanar non-concurrent forces are those forces which __________ at one point, but their lines of action lie on the same plane.
Meet
Do not meet
Either A or B
None of these
The law of motion involved in the recoil of gun is
Newton's first law of motion
Newton's second law of motion
Newton's third law of motion
None of these
In the shown figure, the tension (T) in the string will be 
m₁. m₂. g/(m₁ + m₂)
2m₁. m₂. g/(m₁ + m₂)
(m₁ + m₂)/ m₁. m₂. g
(m₁ + m₂)/2m₁. m₂. g
In a framed structure, as shown in the below figure, the forces in the members AB and BC are respectively 
√3. W (tensile) and 2W (compressive)
2W (tensile) and √3. W (compressive)
2√3. W (tensile) and 2√3. W (compressive)
None of the above
The centre of gravity a T-section 100 mm × 150 mm × 50 mm from its bottom is
50 mm
75 mm
87.5 mm
125 mm
Which is the correct statement about law of polygon of forces?
If any number of forces acting at a point can be represented by the sides of a polygon taken in order, then the forces are in equilibrium
If any number of forces acting at a point can be represented in direction and magnitude by the sides of a polygon, then the forces are in equilibrium
If a polygon representing forces acting at a point is closed then forces are in equilibrium
If any number of forces acting at a point can be represented in direction and magnitude by the sides of a polygon taken in order, then the forces are in equilibrium