**Balanced Force**

If the resultant of all the forces is zero, the forces are called balanced forces.Eg: Two springs X and Y are tied to the two opposite forces of a block. If we apply a force by pulling the string X, the block will move to the right. Simarly if we pull the string Y, the block will move towards the left side. bu if the block is pulled from both the sides with equal forces, the block will not move.

**Unbalanced Forces**

If the resulyant of all the forces acting on a body is not zero, the forces are called unbalanced forces.When unbalanced force act on a body, they produce a change in it's state of rest or of uniform motion. that is unbalanced forces can move a stationary body or they can stop a moving body.

first law of motion

An object at rest or in uniform motion will remain at rest or in uniform motion unless an unbalanced force act upon it.

In other words, all objects resist a chnge in their stateof motion. in a qualitiative way, the tendensy of undisturbed objects to stay at rest or to keep moving with the same velocity is called inertia.

**Momentum**:

The total quantity of motion contained in a body is known as it's momentum.It is a vector quantity and is denoted by p.

Mathematical expression for momentum is

p = mv

**Second Law Of Motion:**

Te rate of change of momentum of an object is propotiona to the applied unbalanced force in the direction of forcs.

Where p is momentum, 'm' is mass of the body and 'v' is the veloity of the body.

According to the third law of motion by newton we apply force whoch is devided propotional to the momentum.

The Concept Of Momentun

Momentum is a better quanyity that is define as the product of mass and velocity.

deravation of second law of motiom

F=applied force

p1=initial momentum

p2=final momentum

u=initial velocity

v=final velocity

t=time

m=mass in kg.

k=constant

Momentum= p = mass*velocity

p = mv

p = kgms

2nd law

F is propotional to p2 - p1/t

is propotional to mv-mu/t

is propotional to m(v-u/t)

is propotional to m*a

F= Kma

since K= i

F= ma

or F= ma

kgms^2

Newton (N)

**third law of motion**

According to this Law each And every action has an equal and opposite reaction.

Important points regarding third law of motion:-

The action and reaction are forces that act in opposite direction.

Boyh the forces occures simultaneously.

Action and reaction are forces which are always equal to each other.

**law of conservation of momentum**

When two bodied collide with each other the total momentum before collision is equal to the total momentum after collision.

We will now derive this law by newtons third law of motion.

mA= mass of ball A

mB= mass of ball B

UA= initial velocity of ball

UB= initial velocity of ball B

VA= final velocity of ball A

VB= final velocity of ball B

t= time of collision

FAB= force of A on B

FBA= force of B on A

FAB = rate of change of momentum

ma(VA-UA)

FBA = mB(VB-UB)

According to third law of motion

FAB = FBA

mA(VA-Ua) = mBNB + mBUB

mAVA + mBVB = mAUA + mBUB