LAWAS OF MOTION FIRST LAW SECOND LAW THIRD LAW OF MOTION

 MOMENTUM:-

          The quantity of motion passed by a body is known as momentum. It is measured by the product of the mass of the body and its velocity. 

                                  Momentum = mass multiply velocity

                                           P = mv

                                    Si unit= kg.m/s

                                   other unit= slug.ft/s

             momentum is a vector quantity and product of mass a scalar quantity  

In our daily life, we experience that the effect product by a heavy body moving with a certain velocity on hitting a certain object is much more than that produced by a lighter body moving with the same velocity. This is because the truck has more mass and hence more momentum than a bicycle.

NEWTONS LAWS OF THE MOTION

The great scientist Issac Newton formulated the there laws governing motion of body and effect of force causing the motion.

  NEWTONS LAW FIRST LAW OF THE MOTIONS 

Newtons' first law of motion states that everybody continues in its states of rest or uniform motion in a straight line unless it is compelled by some external force to change that state. 

       An object at rest remains at rest and an object in motion remains in motion with the same speed and direction.

According to this law, nobody in this universe can change its state of rest or of uniform motion without the help of some external force. A body at rest will remain at rest unless some external force is applied to set it in motion.

Thus the first law of motion gives the definitions of force. Force may be defined as that agent which changer or changes or tend to change the state of rest or of uniform motion of a body.

This first law of motion is also known as the law of inertia. Inertia is the property of a body by virtue of which the body tries to remain in its existing state of uniform motion. Inertia depends upon the mass of the body. More is the mass of the body, more is inertia

NEWTONS LAW SECOND LAW OF MOTION

Newtons second law of motion states that the rate of change of momentum is directly proportional to the applied force and takes place in the direction of application of force, 

                                             

                 Body of mass =m

                 Changes its velocity = u,v

              Time= t

                  Force= f

                The initial momentum of the body= mu

               Final momentum of the body = mv 

               Change in momentum of the body = mu- mv

     now        Rate of change of momentum=  change in momentum \  time

                             =    mv-mu\  t

                              =  m(v-u\ t)

                               =  ma 

a=    Unifrom acceleration of the body 

                    F directly proportional     ma

                     F=K ma      K= constant

               Acceleration in a body of unit mass

            m=1   a=1 f=1

                    1=k 1 1

                  k=1   

hence           f = ma 

NEWTONS LAW THIRD LAW OF THE MOTION

    Newtons third law of motion states that to every action there is an equal and opposite reaction. By action is meant the force which a body exerts on another, whereas the reaction means equal and opposite force which the second body exerts on the first . This law, therefore states that a force always occurs in pair, each pair consisting of two equal and opposite forces 

     exmple-   

         1    In order to swim, a swimmer pushes the water backwards and the reaction of water pushes the swimmer forwards 

2  Whene a bullet is fired from a gun, the bullet moves out with a great velocity and the reaction of the bullet give an unpleasant shock to the man holding the gun in the opposite direction,