NEWTON’S LAWS OF MOTION

 

NEWTON’S LAWS OF MOTION

(Linear Motion)

 

-                      Statement of laws

 

Newton’s first Law         -           The law of Inertia “Every body at rest, or moving with constant velocity in a straight line, will continue in that state unless compelled to change by an external force exerted upon it”.

 

Inertia       -           It is the property of a body, which resist reluctance to change whatever it is doing is known as its Inertia”.

Mass         -           is the quantitative measure of Inertia. Mass reflect the quantity of matter present in an object of which it is composed.

Application          -           easier to alter the motion of a running body who has relative small mass.

MKS         -           Mass is measured in k.g.

 

Force        -           “Force is the effect or influence which one body experience over the other”

                              It may be pull or push effect which different force may bring out a change in state of Motion.

Force has three characteristic

 

IInd Law of Motion        (Law of acceleration)

“ The acceleration of a body is proportional to the force causing it and take place in the direction in which the force act”.

“Rate of change of momentum is directly proportional to the force applied and take place is same direction in which force applied”.

Concept of Momentum   -           The quality of motion possessed by the object or it is product of mass and velocity of the body.

 

M  =  MU

M  =  kg.

V  = M/SC

 

Unit of measurement for M = kg m/sec.

Second law is fully expressed  by the equation.

F  =  M  a.  =  a  =  F

                               M

i)                   certain mass  =  acceleration is greater . Greater the law.

ii)                 Certain force  =   Greater the mass, less the acceleration a longer time. It will take to change its velocity.

 

It applies the rate of change of momentum is equal to applied force.

 

Initial momentum  =  Mu

Final movement  =  Mv

Change in momentum  =  Mv -- Mu

Time take                    =  t

Rate of change of momentum  =  Mv – Mu

                                                            T

IV State of problem

If F is force applied the rate of F µ Mv – Mu

                                                               t

or  F  µ m ( v  -  u)      (a= u – v)

                        t                     t

or         F  µ m  a

F  = k m a

If k = 1

Then  F = ma

 

Force is the basis for mass and acceleration. Since mass remain constant. The actual factor for causing increase or decrease of force is the velocity.

                                   

F = M   

 

 

So IInd law, we can say if quicker accel  is require in change in velocity – greater amount of force is needed.

F & V are directly related to each other

 

¬  Mass provide additional force called momentum force. You can have greater momentum force only when you have move muscular force. Ex. – Thrower, Jumper etc.

 

IIIrd law  -  Law of Reaction

 

 “To every action force, there is an equal and opposite reaction force”.

    Ex.  -  human location

It is the reaction force of the ground which makes the body move forward. So concepts of reaction force is based on  the action force of the body. He applied action  force to ground & ground gives equal & opposite reaction force which make the body move forward. Actually speaking laws found its application in all the sports.

  Reaction

                                                       

 force

 

    Action

 

            Force

 

 

 

Horizontal Distance Running

 

Vertical force should be only for counter action of full of gravity. If it is more                action take place

Application of Newton’s laws of Motion

 

Ist Law of Motion   or Law of Inertia State & Dynamic

 

Application  -  A ball rolling on ground  -  should continue but stop itself after covering some distance . It is due to -  friction force and air resistance force applied on the object in opposite direction of its motion or by any gravitational pull exert on it.

Effect of Inertia

1-                  Getting down from a running train

2-                  Emergency break by bus driver

3-                  Horse stop – rider fall

4-                  Tide boat (Motion)

 

To over come static inertia  is always more need.  More force  is needed – big muscles of body should be used for caning inertia.

IInd -  a base ball pitcher which have more momentum when it throw the ball with greater force and the body follows the direction of line of application of force at the time of release.

-           A cricket better – do the follow throw in the direction of the force applied.

F  =  m a

Mass is the quantitative of Inertia

            As force applied to change the velocity of the body is proportional to mass of the body. Therefore baseball and tennis ball thrower with certain equal amount of velocity more force is required to change the velocity of base ball than of tennis ball.

 

1-         How to increase the speed ?

 

Momentum of body can be increased only when the force is applied in direction of motion otherwise momentum will decrease and gradually will come to zero.

2-         How to stop the ball or catch a ball  ?

 

            F = MV₁                                 

                    t

 

F  x t = Mu1 = force is to be applied in opposite direction for longer period of time.

10 x 2 = 20 m/sc

4 x 5 = 20 m/sc

Cricket ball catching – fielder catch a ball away from the body and bring the hand close to body or some time side of the body – by the time momentum become zero.

All the three laws of motion (linear motion) have their application including daily routine with all sport situations.

Situational demands are to be satisfied for actual application of IIIrd laws.

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2)                  Angular velocity is relationship V₁ = wr = increase r decrease W  or reduce r increase W. e.g. Double Summer Sault.

3)                  Swimming activity movement  can be develop by reduce the radius while going up increase radius while coming down – giant circle .

 

Equation of Uniform Motion

 

 

Q.1      A sprinter accelerates at a constant rate of 4m/sec² for 5 second. What will be the velocity enhanced at the end of 5 sec. & how much distance he may cover till that time.

 

Ans.    v = u + at

            v = 0 + 4m/sec.² x (5 sec)

            4m/sec.² x 5 sec

            u = 20 m/sec

            S = u + ½ at²

            0 + ½(4m/ sec.² x 5² sec

            4 x 25

            ½ (100) m

            S = 50 m

Q.2.     An object release from a height of 19.62 mt. How much time it will take for object to hit the ground and what will be its velocity when it hit the ground?

 

Ans.   S = h = 19.62, 9 = 9.8 m/ sec.² – U=0

            v.² –  u² =2 as

V.² –  0 = 2 x (9.8 m/sec² x 19.62 m)

            V² = 2 x 192.276 m²/sec²

V² = 384.552 m²/sec²

V = 19.61 m/sec

V = U + at

19.61 m/sec = 0 + 9.8 m/sec² x t

19.61 m/sec.  = t 

9.8m

t  =   2.01 sec.

 

 

 

 

 

Q.3 -    An object is projected vertically upward with a velocity of 12 mts /sec. How high object will reach before starting its down ward moment also find out total time of flight of the object from the moment of its projection up to the time it hit the ground?

 

 

Ans.   u = 0 – a = 9.8

V² – u² = 2as

u² – 0 = 2 x 9.8 m/sec x h

12² = 19.6 mt/sec x h

144  m/sec.  = h

19.6 m/sec

            h = 7.35 m

v = u + at

12 = 0 + 9.8 x t

12 = 1.22 = t

9.8

            1.22sec. = t

            Total time taken

            1.22 sec. + 1.22sec.=2.44 sec.