The maximum efficiency of a screw jack is
(1 - sinφ)/(1 + sinφ)
(1 + sinφ)/(1 - sinφ)
(1 - tanφ)/(1 + tanφ)
(1 + tanφ)/(1 - tanφ)
Correct Answer :
A. (1 - sinφ)/(1 + sinφ)
Related Questions
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
Which of the following statement is correct in connection with projectiles?
A path, traced by a projectile in the space, is known as trajectory.
The velocity, with which a projectile is projected, is known as the velocity of projection.
The angle, with the horizontal, at which a projectile is projected, is known as angle of projection.
All of the above
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
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
D' Alembert's principle is used for
Reducing the problem of kinetics to equivalent statics problem
Determining stresses in the truss
Stability of floating bodies
Designing safe structures
Tension in the cable supporting a lift is more when the lift is moving __________ with an acceleration.
Upwards
Downwards
Horizontal
None of these
The minimum force required to slide a body of weight W on a rough horizontal plane is
W sinθ
W cosθ
W tanθ
None of these
In a framed structure, as shown in the below figure, the force in the member BC is 
W/√3 (compression)
W/√3 (tension)
2W/√3 (compression)
2W/√3 (tension)
The Cartesian equation of trajectory is (where u = Velocity of projection, α = Angle of projection, and x, y = Co-ordinates of any point on the trajectory after t seconds.)
y = (gx²/2u² cos²α) + x. tanα
y = (gx²/2u² cos²α) - x. tanα
y = x. tanα - (gx²/2u² cos²α)
y = x. tanα + (gx²/2u² cos²α)
From a circular plate of diameter 6 cm is cut out a circle whose diameter is a radius of the plate. Find the e.g. of the remainder from the centre of circular plate
0.5 cm
1.0 cm
1.5 cm
2.5 cm
The amplitude is always __________ radius of the circle.
Equal to
Less than
Greater than
None of these
Mass moment of inertia of a thin rod about its one end is __________ the mass moment of inertia of the same rod about its midpoint
Same as
Twice
Thrice
Four times
The centre of percussion of a solid cylinder of radius r resting on a horizontal plane will be
r/2
2r/3
r/A
3r/2
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
The total motion possessed by a body, is called
Impulsive force
Mass
Weight
Momentum
The length of a second's pendulum is
94.9 cm
99.4 cm
100 cm
101 cm
The moment of inertia of a thin rod of mass m and length l, about an axis through its centre of gravity and perpendicular to its length is
ml2/4
ml2/ 6
ml2/8
ml2/12
Joule is the unit of
Force
Work
Power
Velocity
A circular hole of 50 mm diameter is cut out from a circular disc of 100 mm diameter as shown in the below figure. The centre of gravity of the section will lie 
In the shaded area
In the hole
At O
None of these
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 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
Which of the following is a vector quantity?
Energy
Mass
Momentum
Angle
Coulomb friction is the friction between
Bodies having relative motion
Two dry surfaces
Two lubricated surfaces
Solids and liquids
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
The matter contained in a body, is called
Impulsive force
Mass
Weight
Momentum
The forces which meet at one point, but their lines of action __________ on the same plane, are Known as non-coplanar concurrent forces.
Lie
Do not lie
Either A or B
None of these
If a number of forces act simultaneously on a particle, it is possible
Not a replace them by a single force
To replace them by a single force
To replace them by a single force through C.G.
To replace them by a couple
In actual machines
Mechanical advantage is greater than velocity ratio
Mechanical advantage is equal to velocity ratio
Mechanical advantage is less than velocity ratio
Mechanical advantage is unity
The C.G. of a right circular solid cone of height h lies at the following distance from the base
h/2
J/3
h/6
h/4
According to principle of moments
If a system of coplanar forces is in equilibrium, then their algebraic sum is zero
If a system of coplanar forces is in equilibrium, then the algebraic sum of their moments about any point in their plane is zero
The algebraic sum of the moments of any two forces about any point is equal to moment of the resultant about the same point
Positive and negative couples can be balanced