A heavy ladder resting on floor and against a vertical wall may not be in equilibrium, if
The floor is smooth, the wall is rough
The floor is rough, the wall is smooth
The floor and wall both are smooth surfaces
The floor and wall both are rough surfaces
Correct Answer :
C. The floor and wall both are smooth surfaces
Related Questions
If the masses of both the bodies, as shown in the below figure, are reduced to 50 percent, then tension in the string will be 
Same
Half
Double
None of these
The equivalent length of a simple pendulum which gives the same frequency as compound pendulum is
h/(kG² + h²)
(kG² + h²)/h
h²/(kG² + h²)
(kG² + h²)/h²
The algebraic sum of moments of the forces forming couple about any point in their plane is
Equal to the moment of the couple
Constant
Both of above are correct
Both of above are wrong
A semicircular disc rests on a horizontal surface with its top flat surface horizontal and circular portion touching down. The coefficient of friction between semi circular disc and horizontal surface is μ. This disc is to be pulled by a horizontal force applied at one edge and it always remains horizontal. When the disc is about to start moving, its top horizontal force will
Remain horizontal
Slant up towards direction of pull
Slant down towards direction of pull
None of the above
The centre of gravity of a semi-circle lies at a distance of __________ from its base measured along the vertical radius.
3r/ 8
4r/ 3π
8r/3
3r/4π
A machine having an efficiency greater than 50%, is known as
Reversible machine
Non-reversible machine
Neither reversible nor non-reversible machine
Ideal machine
Two bodies of masses m1 and m2 are hung from the ends of a rope, passing over a frictionless pulley as shown in the figure below. The acceleration of the string will be 
g (m1 - m2)/(m1 + m2)
2g (m1 - m2)/(m1 + m2)
g (m1 + m2)/(m1 - m2)
2g (m1 + m2)/(m1 - m2)
In the lever of third order, load W, effort P and fulcrum F are oriented as follows
W between P and F
F between W and P
P between W and F
W, P and F all on one side
The resultant of two forces P and Q acting at an angle θ is
√(P² + Q² + 2PQ sinθ)
√(P² + Q² + 2PQ cosθ)
√(P² + Q² - 2PQ cosθ)
√(P² + Q² - 2PQ tanθ)
The range of a projectile is maximum, when the angle of projection is
30°
45°
60°
90°
The unit of force in S.I. units is
kilogram
Newton
Watt
Dyne
If the body falls freely under gravity, then the gravitational acceleration is taken as
+8.9 m/s2
-8.9 m/s2
+9.8 m/s2
-9.8 m/s2
Center of percussion is
The point of C.G.
The point of metacenter
The point of application of the resultant of all the forces tending to cause a body to rotate about a certain axis
Point of suspension
The force induced in the string AB due to the load W, as shown in the below figure is 
W sinθ
W cosθ
W secθ
W cosecθ
The angle between two forces when the resultant is maximum and minimum respectively are:
0° and 180°
180° and 0°
90° and 180°
90° and 0°
A body will begin to move down an inclined plane if the angle of inclination of the plane is _________ the angle of friction.
Equal to
Less than
Greater than
None of these
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 term 'Centroid' is
The same as centre of gravity
The point of suspension
The point of application of the resultant of all the forces tending to cause a body to rotate about a certain axis
None of the above
The acceleration of a particle moving with simple harmonic motion is __________ at the mean position.
Zero
Minimum
Maximum
None of these
Moment of inertia of a hollow rectangular section as shown in the below figure about X-X axis, is 
(BD³/12) - (bd³/12)
(DB³/12) - (db³/12)
(BD³/36) - (bd³/36)
(DB³/36) - (db³/36)
A framed structure is perfect if it contains members equal to
2n³
2n
n²
3n² Where n = number of joints in a frame
The force required to move the body up the plane will be minimum if it makes an angle with the inclined plane __________ the angle of friction.
Equal to
Less than
Greater than
None of these
When the spring of a watch is wound, it will possess
Strain energy
Kinetic energy
Heat energy
Electrical energy
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 M.I. of hollow circular section about a central axis perpendicular to section as compared to its M.I. about horizontal axis is
Same
Double
Half
Four times
Joule is the unit of
Force
Work
Power
Velocity
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
(2/3) Ml2
(1/3) Ml2
(3/4) Ml2
(1/12) Ml2
In the shown figure, if the angle of inclination of the plane is increased, then acceleration of the system will 
Increase
Decrease
Remain the same
None of these
The moment of the force P about O as shown in the below figure is 
P × OA
P × OB
P × OC
P × AC
Which of the following is not the unit of energy?
kg m
kcal
Watt
Watt hours