A machine having an efficiency greater than 50%, is known as
Reversible machine
Non-reversible machine
Neither reversible nor non-reversible machine
Ideal machine
Correct Answer :
A. Reversible machine
Related Questions
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 
h [(2a + b)/(a + b)]
(h/2) [(2a + b)/(a + b)]
(h/3) [(2a + b)/(a + b)]
(h/3) [(a + b)/(2a + b)]
The resultant of two equal forces P making an angle θ, is given by
2P sinθ/2
2P cosθ/2
2P tanθ/2
2P cotθ/2
The centre of gravity of an isosceles triangle with base (p) and sides (q) from its base is
[√(4p² - q²)]/6
(4p² - q²)/6
(p² - q²)/4
(p² + q²)/4
The moment of inertia of a square of side (a) about an axis through its centre of gravity is
a4/4
a4/8
a4/12
a4/36
Two non-collinear parallel equal forces acting in opposite direction
Balance each other
Constitute a moment
Constitute a couple
Constitute a moment of couple
In a framed structure, as shown in the below figure, the force in the member AB is __________ the force in member AC. 
Half
Equal to
Double
None of these
The C.G. of a plane lamina will not be at its geometrical centre in the case of a
Right angled triangle
Equilateral triangle
Square
Circle
A particle moves along a straight line such that distance (x) traversed in t seconds is given by x = t² (t - 4), the acceleration of the particle will be given by the equation
6t² - 8t
3t² + 2t
6f - 8
6f - 4
Which one of the following statements is not correct?
The tangent of the angle of friction is equal to coefficient of friction
The angle of repose is equal to angle of friction
The tangent of the angle of repose is equal to coefficient of friction
The sine of the angle of repose is equal to coefficient to friction
Moment of inertia of a circular section about its diameter (d) is
πd3/16
πd3/32
πd4/32
πd4/64
A projectile is fired at an angle θ to the vertical. Its horizontal range will be maximum when θ is
0°
30°
45°
60°
The velocity ratio in case of an inclined plane inclined at angle θ to the horizontal and weight being pulled up the inclined plane by vertical effort is
sinθ
cosθ
tanθ
cosecθ
Two like parallel forces are acting at a distance of 24 mm apart and their resultant is 20 N. It the line of action of the resultant is 6 mm from any given force, the two forces are
15 N and 5 N
20 N and 5 N
15 N and 15 N
None of these
If n = number of members and y = number of joints, then for a perfect frame, n = ?
1/2
2/3
3/2
2/4
Which of the following are vector quantities?
Angular displacement
Angular velocity
Angular acceleration
All of these
The acceleration of a particle moving with simple harmonic motion, at any instant is given by
ω.y
ω2.y
ω2/y
ω3.y
Coefficient of friction is the
Angle between normal reaction and the resultant of normal reaction and the limiting friction
Ratio of limiting friction and normal reaction
The friction force acting when the body is just about to move
The friction force acting when the body is in motion
The impact between two lead spheres is approximately equal to an __________ impact.
Elastic
Inelastic
Solid
None of these
Moment of inertia of a hollow circular section, as shown in the below figure about X-axis, is 
π/16 (D² - d²)
π/16 (D³ - d³)
π/32 (D⁴ - d⁴)
π/64 (D⁴ - d⁴)
The angle which an inclined plane makes with the horizontal when a body placed on it is about to move down is known as angle of
Friction
Limiting friction
Repose
Kinematic friction
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
Moment of inertia of a triangular section of base (b) and height (h) about an axis passing through its C.G. and parallel to the base, is
bh3/4
bh3/8
bh3/12
bh3/36
The force induced in the string BC due to the load W as shown in the below figure is 
W sinθ
W cosθ
W tanθ
W cotθ
The weight of a body is due to
Gravitational pull exerted by the earth
Forces experienced by body in atmosphere
Force of attraction experienced by particles
Gravitational force of attraction towards the centre of the earth
In ideal machines, mechanical advantage is __________ velocity ratio.
Equal to
Less than
Greater than
None of these
The ratio of static friction to dynamic friction is always
Equal to one
Less than one
Greater than one
None of these
Whenever a force acts on a body and the body undergoes a displacement, then
Work is said to be done
Power is being transmitted
Body has kinetic energy of translation
None of these
The maximum height of a projectile on a horizontal plane, is
u² sin²α/2g
u² cos²α/2g
u² sin²α/g
u² cos²α/g
The overturning of a vehicle on a level circular path can be avoided if the velocity of vehicle is __________ √(gra/h)
Less than
Greater than
Equal to
None of these
The unit of force in S.I. units is
kilogram
Newton
Watt
Dyne