1. Force
Units:
2. Newton’s Laws of Motion
3. System
4. Equilibrium of a Particle
- Static equlibrium:
- Dynamic equlibrium:
A pull or push which changes or tends to change
the state of rest or of uniform motion or direction
of motion of any object is called force.
newton and 2
kg.m
s
(MKS System)
1 newton = 10^5 dyne
(I) First law of motion
Each body continues to be in its state of rest or
of uniform motion in a straight line unless acted
upon by some external force.
(II) Second law of motion
The force acting on a body is equal to rate of
change of momentum
d p d dv dm
F mv m v
dt dt dt dt
dm
F ma 0
dt
Where p m v
, p
= Linear momentum.
(III)Third law of motion
To every action, there is always an equal and
opposite reaction.
Two or more than two objects which interact with
each other form a system.
Classification of forces on the basis of boundary
of system :
(I) Internal Forces
Forces acting each with in a system among its
constituents.
(II) External forces
Forces exerted on the constituents of a system
by the outside surroundings are called as
external forces.
For a particle to be in equlibrium the net external
force acting on the particle must be zero.
In translatory motion, equlibrium is of two types:
In this Fnet 0
and body is
at rest.
In this Fnet 0
and body
moves with uniform velocity.
Newton’s IInd law w.r.to both inertial & non-inertial
frames are
Fextma
(w.r.to inertial frame)
F F maext s r
(w.r.to non-inertial frame)
Fext
external force
Fs
Pseudo force (Fs=mas)
as Acceleration of non inertial frame
a
Acceleration of the body w.r.to ground frame
ar
Acceleration of the body w.r.to non-inertial
frame
4. Newtons Laws of Motion, Friction & Circular Motion
