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
Correct Answer :
C. Proportional to velocity of sliding
Related Questions
A lead ball with a certain velocity is made to strike a wall, it falls down, but rubber ball of same mass and with same velocity strikes the same wall, it rebounds. Select the correct reason from the following:
Both the balls undergo an equal change in momentum
The change in momentum suffered by rubber ball is more than the lead ball
The change in momentum suffered by rubber ball is less than the lead ball
None of the above
A body of mass m moving with a constant velocity v strikes another body of same mass moving with same velocity but in opposite direction. The common velocity of both the bodies after collision is
v
2v
4v
8v
Work done is said to be zero, when
Some force acts on a body, but displacement is zero
No force acts on a body but some displacement takes place
Either (A) or (B)
None of the above
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 moment of inertia of a thin disc of mass m and radius r, about an axis through its centre of gravity and perpendicular to the plane of the disc is
mr2/2
mr2/4
mr2/6
mr2/8
Kinetic friction is the
Tangent of 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 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
The time of flight (t) of a projectile on an upward inclined plane is (where u = Velocity of projection, α = Angle of projection, and β = Inclination of the plane with the horizontal.)
t = g cos β/2u sin (α - β)
t = 2u sin (α - β)/g cos β
t = g cos β/2u sin (α + β)
t = 2u sin (α + β)/g cos β
The motion of a wheel of a car is
Purely translation
Purely rotational
Combined translation and rotational
None of these
Moment of inertia of a circular section about an axis perpendicular to the section is
πd3/16
πd3/32
πd4/32
πd4/64
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
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
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
Which of the following is not the unit of distance?
Angstrom
Light year
Micron
Milestone
A cable with a uniformly distributed load per horizontal meter run will take the following shape
Straight line
Parabola
Hyperbola
Elliptical
The maximum frictional force, which comes into play, when a body just begins to slide over the surface of the other body, is known as
Static friction
Dynamic friction
Limiting friction
Coefficient of friction
The velocity ratio for the third system of pulleys is
n
n²
2n
2n - 1
One kg force is equal to
7.8 N
8.9 N
9.8 N
12 N
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
The unit of work in S.I. units is
Newton
erg
kg-m
joule
Which of the following is not the unit of energy?
kg m
kcal
Watt
Watt hours
The linear acceleration (a) of a body rotating along a circular path of radius (r) with an angular acceleration of α rad/s2, is
a = α/ r
a = α.r
a = r / α
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 slope on the road surface generally provided on the curves is known as
Angle of friction
Angle of repose
Angle of banking
None of these
On a ladder resting on smooth ground and leaning against vertical wall, the force of friction will be
Towards the wall at its upper end
Away from the wall at its upper end
Upwards at its upper end
Downwards at its upper end
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
The process of finding out the resultant force is called __________ of forces.
Composition
Resolution
Decomposition
None of these
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 length of a second's pendulum is
94.9 cm
99.4 cm
100 cm
101 cm
The coefficient of friction depends on
Area of contact
Shape of surfaces
Strength of surfaces
Nature of surface