According to Lamis theorem
The three forces must be equal
The three forces must be at 120° to each other
The three forces must be in equilibrium
If the three forces acting at a point are in equilibrium, then each force is proportional to the sine of the angle between the other two
Correct Answer :
D. If the three forces acting at a point are in equilibrium, then each force is proportional to the sine of the angle between the other two
Related Questions
The force, by which the body is attracted, towards the centre of the earth, is called
Impulsive force
Mass
Weight
Momentum
Two balls of equal mass and of perfectly elastic material are lying on the floor. One of the balls with velocity v is made to strike the second ball. Both the balls after impact will move with a velocity
v
v/2
v/4
v/8
The unit of work or energy in S.I. units is
Newton
Pascal
Watt
Joule
The ratio of limiting friction and normal reaction is known as
Coefficient of friction
Angle of friction
Angle of repose
Sliding friction
The three forces of 100 N, 200 N and 300 N have their lines of action parallel to each other but act in the opposite directions. These forces are known as
Coplanar concurrent forces
Coplanar non-concurrent forces
Like parallel forces
Unlike parallel forces
The motion of a wheel of a car is
Purely translation
Purely rotational
Combined translation and rotational
None of these
A screw jack used for lifting the loads is
A reversible machine
A non-reversible machine
An ideal machine
None of these
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
In actual machines, mechanical advantage is __________ velocity ratio.
Equal to
Less than
Greater than
None of these
Two like parallel forces are acting at a distance of 24 mm apart and their resultant is 20 N. It the line of action of the resultant is 6 mm from any given force, the two forces are
15 N and 5 N
20 N and 5 N
15 N and 15 N
None of these
The mechanical advantage of a lifting machine is the ratio of
Distance moved by effort to the distance moved by load
Load lifted to the effort applied
Output to the input
All 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
If a suspended body is struck at the centre of percussion, then the pressure on die axis passing through the point of suspension will be
Maximum
Minimum
Zero
Infinity
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
The moment of a force
Is the turning effect produced by a force, on the body, on which it acts
Is equal to the product of force acting on the body and the perpendicular distance of a point and the line of action of the force
Is equal to twice the area of the triangle, whose base is the line representing the force and whose vertex is the point, about which the moment is taken
All of the above
The resultant of the following three couples 20 kg force, 0.5 m arm, +ve sense 30 kg force, 1 m arm, -ve sense 40 kg force, 0.25 m arm, +ve sense having arm of 0.5 m will be
20 kg, -ve sense
20 kg, + ve sense
10 kg, + ve sense
10 kg, -ve sense
The periodic time of one oscillation for a simple pendulum is (where l = Length of the pendulum.)
(1/2π). √(l/g)
(1/2π). √(g/l)
2π. √(l/g)
None of these
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
Two non-collinear parallel equal forces acting in opposite direction
Balance each other
Constitute a moment
Constitute a couple
Constitute a moment of couple
A rubber ball is dropped from a height of 2 m. If there is no loss of velocity after rebounding, the ball will rise to a height of
1 m
2 m
3 m
4 m
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
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
The acceleration of a body sliding down an inclined surface is
g sinθ
g cosθ
g tanθ
None of these
In a single threaded worm and worm wheel, the number of teeth on the worm is 50. The diameter of the effort wheel is 100 mm and that of load drum is 50 mm. The velocity ratio is
50
100
200
400
A framed structure is imperfect, if the numbers of members are __________ (2j - 3).
Equal to
Less than
Greater than
Either (B) or (C)
The process of finding out the resultant force is called __________ of forces.
Composition
Resolution
Decomposition
None of these
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
Moment of inertia is the
Second moment of force
Second moment of area
Second moment of mass
All of these
The periodic time of a particle with simple harmonic motion is __________ proportional to the angular velocity.
Directly
Inversely
Square root
None of these
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