# 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 × ****Δ****t**** I = F × ****Δ**

**Derivation of the Formula**

** I = refers to the impulse**** F = refers to the force of the object**** Δ****t**** = 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 = ****Δ****p****⃗**** **** = ****p****⃗**** ****final**** – ****p****⃗**** ****initial**

**Impulse (I) = F x t = m(v-u).**

**Si unit= Nsec. And kgm/sec.**

**Dimension = MLT^-1**