Definition of force,types of forces,law of forces,system of forces, moment of a force, couple,moment of a couple,types of moments,features of couple and principle of moments.
3. Forces & moments
Rajesh P V
Carmel Polytechnic college, Alappuzha, Kerala,
India,
fridayends13@gmail.com
+919497336713
4. Ts i- 3013- contents...
SPECIFIC OUTCOME
MODULE – I
1.1.0 Understand Moment of a force
1.1.1 Identify the various types of forces
1.1.2 State the principle of moments
CONTENT DETAILS
MODULE – I
Forces and Moments
Definition of force –types of forces, Moment of force – types
of moments – principle of moments (proof
not required)
5. FORCE
MATTER - The substance of which all the things are
composed.
BODY - A limited quantity of matter occupying a
certain portion of the space.
MASS - The quantity of matter contained in a body.
6. FORCE...
Force is anything which changes or tends to change the
state of rest or of uniform motion along a straight line.
Force is the action of one body on any other body.
Force is the product of mass (m) and acceleration (a)
F = m x a
Force is a vector quantity.
Unit-Newton (N) , kN, kg m/s2, dyne(cgs unit), pound
force etc.
(PVC)
7. FORCE...
Some examples of force are:
Gravitational force,
Electric force,
Magnetic force,
Nuclear force,
Frictional force etc.
9. TYPEs OF FORCEs
.CONTACT FORCES.
Force which represent the result of physical contact
between two objects that is one of the object exerts force
on the other is called contact forces.
Forces which act on a body either directly or through a
medium are called contact forces.
Eg: Stretching of a spring balance, kicking of football, etc.
10. Types of forces...
NON CONTACT FORCE
Forces which act through spaces without
making direct contact with the body are called
non-contact forces.
13. PRINCIPLE OF TRANSMISSIBILITY
External effect of a force is independent of its point of
application.
Or
External effect of a force on a rigid body is the same for all
points of application along its line of action.
14. RESOLUTION OF FORCE
The process of splitting up the given force into a number of
components , without changing its effect on the body is
called resolution of a force.
A force is, generally, resolved along two mutually
perpendicular directions.
Horizontal component , Fx=F cosθ
Vertical component,Fy =F sinθ
(PVC)
18. EQUILIBRANT
Equilibrant- It is a single force which is equal in
magnitude but opposite in direction to the resultant of
a system of forces.
19. system of forces
Parallel forces
Non parallel forces
Like parallel forces
Unlike parallel forces
Concurrent forces
Non concurrent forces
Collinear forces
Non collinear forces
Coplanar forces
Non coplanar forces
Coplanar concurrent forces
Coplanar non concurrent forces
Coplanar like parallel forces
Coplanar unlike parallel forces
Non coplanar concurrent forces
Non coplanar non concurrent forces, etc.
20. Law of forces
Triangle law of forces
Parallelogram law of forces
Polygon law of forces
21. Triangle law of forces
If two forces are represented both in magnitude and
direction by the adjacent sides of a triangle taken in
order, then their resultant is represented by the third
side of the triangle taken in the reverse order.
22. Parallelogram law of forces
If two forces are represented both in magnitude
and direction as the adjacent sides of a
parallelogram drawn from a point, then the
resultant is represented by the diagonal of the
parallelogram drawn from the same point.
23. polygon law of forces
If any number of forces, acting on a particle , be
represented ,in magnitude and direction by the
sides of a polygon ,taken in order, then the forces
will be in equilibrium.
24. Moment of a force
Moment of a force about a given point is the turning effect
of the force about the point and is measured as the the
product of that force and the perpendicular distance
between the point and the line of action of the force.
Moment of a force =force x the perpendicular distance
between the point and the line of action of the force.
= F x d
Unit -Newton metre (Nm) .
(PVC)
27. TYPES OF MOMENTS
CLOCKWISE MOMENT
If force acting on a body has the tendency to rotate the body in
clockwise direction the moment produced is known as
clockwise moment these are taken as negative (-)
28. TYPES OF MOMENTS
ANTICLOCKWISE MOMENT
If a force acting on a body has the tendency to rotate the body
in anticlockwise direction, then the moment as produced is
called anticlockwise moment its taken as positive (+)
29. principle of moments
(varignon’s theorem)
The Moment of a force about any point is equal to the
algebraic sum of the moments of its components
about the same point.
Or
The algebraic sum of the moments of a system of
unequal forces about any point in their plane is equal
to the moment of their resultant about that point.
(PVC)
30. couple
Two equal and unlike parallel forces whose line of
action are different constitute a couple.
Unit - Newton metre (Nm),kNm, kNmm, etc.
Effect of couple is to produce turning moment or
rotation.
31. moment of a couple
The product of one of the two forces forming the
couple and the arm of the couple.
The arm of the couple is the perpendicular distance
between the lines of action of the forces.
Unit - Newton metre (Nm), kNm, kNmm, etc
(PVC)
32. moment of a couple
Arm of the couple = LM
Moment of the couple = Force x Arm of the couple
= F x LM
(PVC)
33. Torque
Moment of the couple is called torque
Unit -Newton metre (Nm), kNm, kNmm, etc
(PVC)
35. MAIN CHARACTERISTICS OF COUPLE
The algebraic sum of the forces, having the couple, is zero.
The algebraic sum of moment of the forces, constituting
couple, about any point is the same, and equal to the moment
of couple itself.
A couple can't be balanced by a single force, but can be
balanced only by a couple, however of opposite sense.
Any number of coplanar couples can be reduced to single
couple, whose magnitude will be equal to algebraic sum of
moments of all the couples.
36. previous questions ..
Define force
What are the different types of forces?
What are the system of forces?
Define moment of a force?
What are the different types of moments?
Define couple?
Define moment of a couple.
State Varignon’s theorem ( State the principle of moments)
What is the arm of the couple?
37. Additional questions ..
Write the unit of 1.)force, 2.)moment of a force, 3.)couple
5.)moment of a couple and 6.)torque.
State principle of transmissibility.
What are the elements (specifications) of force?
State the triangle law of forces.
State the parallelogram law of forces.
State the polygon law of forces.
What is resolution of forces?
Differentiate between resultant and equilibrant.
Define couple?
State Varignon’s theorem ( State the principle of moments)
List the characteristics of couple?
38. References..
1. R.S.Khurmi : Applied Mechanics & Strength of Materials;
S. Chand Publishing
2. M.Chakrabroti : Strength of materials ; S.K Kataria
&sons.
3. R.K.Rajput : Strength of Materials ; S. Chand Publishing
4. S.S.Bhavikatti : Strength of Materials ; Vikas Publishing
House Pvt Ltd,
5.K.N.A.G.K. Manikanta: Theory of structures –I; Radiant
Publishing House