A ladder is resting on a rough ground and leaning against a smooth vertical wall. The force of friction will act
Downward at its upper end
Upward at its upper end
Zero at its upper end
Perpendicular to the wall at its upper end
Correct Answer :
C. Zero at its upper end
Related Questions
Three forces acting on a rigid body are represented in magnitude, direction and line of action by the three sides of a triangle taken in order. The forces are equivalent to a couple whose moment is equal to
Area of the triangle
Twice the area of the triangle
Half the area of the triangle
None of these
One joule is equal to
0.1 N-m
1 N-m
10 N-m
100 N-m
In actual machines, mechanical advantage is __________ velocity ratio.
Equal to
Less than
Greater than
None of these
The time of flight (t) of a projectile on a horizontal plane is given by
t = 2u. sinα/g
t = 2u. cosα/g
t = 2u. tanα/g
t = 2u/g.sinα
The C.G. of a solid hemisphere lies on the central radius 3r
At distance from the plane base 3r
At distance from the plane base 3r
At distance from the plane base 3r
At distance from the plane base
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
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
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 energy possessed by a body, for doing work by virtue of its position, is called
Potential energy
Kinetic energy
Electrical energy
Chemical energy
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
Moment of inertia of a rectangular section having width (b) and depth (d) about an axis passing through its C.G. and parallel to the depth (d), is
db3/12
bd³/12
db³/36
bd³/36
Which of the following is a scalar quantity?
Force
Speed
Velocity
Acceleration
The maximum frictional force which comes into play when a body just begins to slide over another surface is called
Limiting friction
Sliding friction
Rolling friction
Kinematic friction
The bellow figure shows the three coplanar forces P, Q and R acting at a point O. If these forces are in equilibrium, then 
P/sin β = Q/sin α = R/sin
P/sin α = Q/sin β = R/sin
P/sin = Q/sin α = R/sin β
P/sin α = Q/sin = R/sin β
The forces, which meet at one point and their lines of action also lie on the same plane, are known as
Coplanar concurrent forces
Coplanar non-concurrent forces
Non-coplanar concurrent forces
Non-coplanar non-concurrent forces
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 unit of moment of inertia of an area is
kg-m2
kg-m-s2
kg/m2
m4
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
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)
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
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
If u1 and u2 are the velocities of two moving bodies in the same direction before impact and v1 and v2 are their velocities after impact, then coefficient of restitution is given by
(v1 - v2)/(u1 - u2)
(v₂ - v₁)/(u1 - u2)
(u1 - u2)/(v1 - v2)
(u₂ + u₁)/(v₂ + v₁)
Centre of gravity of a solid cone lies on the axis at the height
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 rate of change of momentum is directly proportional to the impressed force, and takes place in the same direction in which the force acts. This statement is known as
Newton's first law of motion
Newton's second law of motion
Newton's third law of motion
None of these
Moment of inertia of a triangular section of base (b) and height (h) about an axis passing through its vertex and parallel to the base, is __________ than that passing through its C.G. and parallel to the base.
Nine times
Six times
Four times
Two times
If a number of forces are acting at a point, their resultant will be inclined at an angle θ with the horizontal, such that
tanθ = ΣH/ΣV
tanθ = ΣV/ΣH
tanθ = ΣV × ΣH
tanθ = √(ΣV + ΣH)
The angular velocity (in rad/s) of a body rotating at N revolutions per minute is
πN/60
πN/180
2πN/60
2πN/180
A body of weight W is required to move up on rough inclined plane whose angle of inclination with the horizontal is α. The effort applied parallel to the plane is given by (where μ = tanφ = Coefficient of friction between the plane and the body.)
P = W tanα
P = W tan (α + φ)
P = W (sinα + μcosα)
P = W (cosα + μsinα)
Which of the following is not the unit of power?
kW (kilowatt)
hp (horse power)
kcal/sec
kcal/kg sec
When the spring of a watch is wound, it will possess
Strain energy
Kinetic energy
Heat energy
Electrical energy