Tissue

 Force:-  

It is defined as the acceleration to move the object from one position to another.
                                               Or 
The push or pull on an object with mass that causes it to change its velocity. Force is an external agent capable of changing the state of rest or motion of a body.
    
                        Force = Mass × Acceleration 
                                F = m × a
Where, the terms are denoted by the following alphabets:-
Force = F, 
Mass = m   and
Acceleration = a

The SI unit of Force is Newton Or Kg-m/s²

Types of Force:-
    (i) Balance Force 
    (ii) Unbalance Force 

(i) Balance Force:-  When the resultant value of both sides of forces applied on the objects is same than          the force is said to be Balance Force. 
In this both the persons have equally applied force so the resultant value is zero.

(ii) Unbalance Force:-   When two opposite forces acting on a body, move a body in the direction of the greater force or forces which brings motion in a body are called as unbalanced forces.

(iii). Frictional force: The force that always opposes the motion of objects is called a force of friction.

First law of motion: 
   An object remains in a state of rest or of uniform motion in a straight line unless acted upon by an external unbalanced force.

Inertia: 
   The natural tendency of an object to resist a change in their state of rest or of uniform motion is called inertia.
The mass of an object is a measure of its inertia.
Its S.I. unit is kg.


The second law of motion: 
   The rate of change of momentum of an object is proportional to the applied unbalanced force in the direction of the force. 

Mathematically, 

Momentum: 
   The momentum of an object is the product of its mass and velocity and has the same direction as that of the velocity. 
It is denoted by P. 
               Momentum = mass × velocity
                                   P = m × v
Its S.I. unit is kg m/s.

Conservation of momentum:
    If the external force on a system is zero, the momentum of the system remains constant i.e., in an isolated system, the total momentum remains conserved.
  Suppose A and B are two balls, they have mass mA and and initial velocities uA and uB as shown in above figure before collision. The two bodies collide and force is exerted by each body. There is change in their velocities due to collision.

   A body with greater mass has greater inertia.
(mAuA + mAuB) is the total momentum of the two balls A and B before collision and (mAvA + mBvB) is their total momentum after the collision.
   The sum of momenta of the two objects before collision is equal to the sum of momentum after the collision, provided there is no external unbalanced force acting on them. This is known as the law of conservation of momentum


Define 1 Newton Force.

    A force of one Newton produces an acceleration of 1 m/s2 on an object of mass 1 kg.
IN. = 1 kg m/s2 (F = ma)
                                 F = 1 × 1 Kg-m/s²
                                 F = 1 Newton.

Third law of motion:
 To every action, there is an equal and opposite reaction and they act on two different bodies.

Example:-