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
Correct Answer :
D. ml2/12
Related Questions
The principle of transmissibility of forces states that, when a force acts upon a body, its effect is
Same at every point on its line of action
Different at different points on its line of action
Minimum, if it acts at the centre of gravity of the body
Maximum, if it acts at the centre of gravity of the body
Centre of gravity of a thin hollow cone lies on the axis at a height of
One-fourth of the total height above base
One-third of the total height above base
One-half of the total height above base
Three-eighth of the total height above the base
The acceleration of a body sliding down an inclined surface is
g sinθ
g cosθ
g tanθ
None of these
A framed structure is imperfect, if the numbers of members are __________ (2j - 3).
Equal to
Less than
Greater than
Either (B) or (C)
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
For a self locking machine, the efficiency must be
Equal to 50 %
Less than 50 %
Greater than 50 %
100 %
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 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
According to parallel axis theorem, the moment of inertia of a section about an axis parallel to the axis through centre of gravity (i.e. IP) is given by(where, A = Area of the section, IG = Moment of inertia of the section about an axis passing through its C.G., and h = Distance between C.G. and the parallel axis.)
IP = IG + Ah2
IP = IG - Ah2
IP = IG / Ah2
IP = Ah2 / IG
Pick up wrong statement about friction force for dry surfaces. Friction force is
Proportional to normal load between the surfaces
Dependent on the materials of contact surface
Proportional to velocity of sliding
Independent of the area of contact surfaces
Non-coplanar non-concurrent forces are those forces which
Meet at one point, but their lines of action do not lie on the same plane
Do not meet at one point and their lines of action do not lie on the same plane
Do not meet at one point but their lines of action lie on the same plane
None of the above
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
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
Which of the following is not the unit of work, energy and heat?
kcal
kg-m
kW-hr
h.p
Non-coplanar concurrent forces are those forces which
Meet at one point, but their lines of action do not lie on the same plane
Do not meet at one point and their lines of action do not lie on the same plane
Meet at one point and their lines of action also lie on the same plane
Do not meet at one point, but their lines of action lie on the same plane
Moment of inertia of a triangular section of base (b) and height (h) about an axis through its base, is
bh3/4
bh3/8
bh3/12
bh3/36
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)
A force while acting on a body may
Change its motion
Balance the forces, already acting on it
Give rise to the internal stresses in it
All 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
Tension in the cable supporting a lift is more when the lift is moving __________ with an acceleration.
Upwards
Downwards
Horizontal
None of these
Moment of inertia of a hollow circular section, as shown in the below figure about an axis perpendicular to the section, is __________ than that about X-X axis. 
Two times
Same
Half
None of these
The skidding away of the vehicle on a level circular path can be avoided if the force of friction between the wheels and the ground is __________ the centrifugal force.
Less than
Greater than
Equal to
None of these
One joule means that
Work is done by a force of 1 N when it displaces a body through 1 m
Work is done by a force of 1 kg when it displaces a body through 1 m
Work is done by a force of 1 dyne when it displaces a body through 1 cm
Work is done by a force of 1 g when it displaces a body through 1 cm
The maximum velocity of a particle moving with simple harmonic motion is
ω
ωr
ω2r
ω/r
When a body of mass moment of inertia I (about a given axis) is rotated about that axis with an angular velocity to, then the kinetic energy of rotation is
Iω
Iω2
0.5 Iω
0.5 Iω2
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
Two coplanar couples having equal and opposite moments
Balance each other
Produce a couple and an unbalanced force
Are equivalent
Cannot balance each other
The centre of percussion is below the centre of gravity of the body and is at a distance equal to
h/kG
h2/kG
kG2/h
h × kG
The bodies which rebound after impact are called
Inelastic bodies
Elastic bodies
Neither elastic nor inelastic bodies
None of these
The acceleration of a particle moving with simple harmonic motion is __________ at the mean position.
Zero
Minimum
Maximum
None of these