Laws Of Motion , Law of Inertia, Impulse and Impulsive Force
Laws Of Motion
Inertia : It is inherent characteristic due to change its condition of motion.
There are three types of inertia. It is scalar quantity
A: Inertia of rest : The opposition of body due to change its state of rest.
B: Inertia of motion: The opposition of body due to change its state of motion.
C: Inertia of direction: It is inability of a body to change its direction of motion.
Important point -
Mass is the measurement of inertia.
Inertia is depend on mass.
Force:
Is push or pull. It changes a condition of motion.
It is a vector quantity.
System of particles:
It is a group of particles having same velocity and fixed distance between them.
Momentum:
It is characteristic of a moving object.
It denoted by P.
P=mv
It is vector quantity
Si unit of momentum is kgm/sec^2.
Newton’s First Law ( Law of Inertia) :
An object stay at rest or motion continue unless an external force is applied on it.
Important points:
It defines inertia, force and mechanical equilibrium, Net acceleration of object is zero.
First law gives definition of force.
Newton Second Law:
Rate of change of momentum is directly proportionate to the net external force is applied on object.
Second law gives quantity of force
F∝ dp/dt
F∝ d(mv)/dt
F∝ mdv/dt. (dv/dt=a)
F∝ ma –eq (i)
F= kma , where k is constant.
If F=1 , m=1 , a=1 then k=1
Putting value of k in equation (i)
Then F= ma.
Si unit of force is
CGS unit = dyne.
One newton =
Force is a vector quantity.
Dimension= MLT^−2.
Second Law : Impulse and Impulsive Force
A large number of force can create in very small interval of time.
Impulse = Force × (final time – initial time)
Impulse = Force × Δt
I = F × Δ
Derivation of the Formula
I = refers to the impulse
F = refers to the force of the object
Δt = refers to the change in time
Since the impulse is a measure of how much the momentum changes as a result of a force acting on it for a period of time. Moreover, an alternative formula for impulse is
Impulse = Δp⃗ = p⃗ final – p⃗ initial
Impulse (I) = F x t = m(v-u).
Si unit= Nsec. And kgm/sec.
Dimension = MLT^-1