Newton law of Motion
• Newton's First Law of Motion
Every body continues in its state of rest or of uniform motion in a straight
line unless an external force acts on it. Newton's first law defines the
principle of the equilibrium of forces, which is the main topic of concern in
statics.
• Newton's Second Law of Motion
The rate of change of momentum of a body is directly proportional to the
force acting on it and takes place in the direction of applied force.
• Newton's Third Law of Motion
To every action, there is an equal and opposite reaction. The forces of action
and reaction between interacting bodies are equal in magnitude, opposite in
direction and collinear. It means that forces always occur in pairs of equal
and opposite forces.
• Principle of Transmissibility of Force
It states that the condition of equilibrium or uniform motion of rigid body
will remain unchanged if the point of application of a force acting on a
rigid body is transmitted to act at any other point along its line of action.
Law of Parallelogram of Force
If two forces acting simultaneously on a body at a point are represented
in magnitude and direction by two adjacent sides of a parallelogram,
then their resultant is represented in magnitude and direction by the
diagonal of a parallelogram which passes through the point of
intersection of the two sides representing the forces.
Triangle Law of Force
“If two forces acting simultaneously on a particle, be represented in
magnitude and direction by the two sides of a triangle, taken in order ;
their resultant may be represented in magnitude and direction by the
third side of the triangle, taken in opposite order.”
Classification of Force System
Force System May Be Classified As Follows :
Force System
Non - Coplanar
Coplanar
Concurrent
Parallel
Like
Non –Concurrent
And
Non Parallel
Unlike
Concurrent
Parallel
Like
Non –Concurrent
And
Non Parallel
Unlike
Force System :
– When a number of forces act simultaneously on a body then
they are said to form a force system.
Depending upon whether the line of action of all the forces
acting on the body lies in the same plane or in different
plane, the force system may be classified as follows :
– Coplanar Force System : If the line of action of all the forces in
the system lies on the same plane then it is called a coplanar
force system.
– Non-coplanar Force System : If the line of action of all the forces
in the system do not lie on the same plane then it is called a
non-coplanar force system.
Concurrent Force System
Parallel Force System
non-concurrent
and non-parallel force system.
RESULTANT OF FORCE SYSTEM
Resultant Force is a single force which replaces
the given force system having the same effect.
Composition of Forces
The process of finding the resultant of forces is
called composition of forces.
Problems on Composition of Forces by
Parallelogram and Triangle Law
Law of Parallelogram of Force
Problem 1
Find the resultant of the given forces.
Triangle Law of Force
Problem 2
Find the resultant of the given forces.
Problem 5
A car is pulled by means of two ropes as shown in Fig. The
tension in one rope is P = 2.6 kN. If the resultant of two forces
applied at O is directed along the x axis of the car. Find the
tension in the other rope and magnitude of the resultant.