SIR ISAAC NEWTON

Sir Isaac Newton ( 1642 – 1726) was an English physicist and mathematician who is widely recognised as one of the most

influential scientists of all time and as a key figure in the scientific revolution.

NEWTON’S LAWS OF MOTION

Sir Isaac Newton gave us 3 Laws Of Motion, They are :

1st Law- Everybody continues in its state of rest or uniform motion in straight line unless compelled by some external force.

2nd Law- The rate of change of momentum of a body is directly proportional to the applied unbalanced force in the direction of force.

3rd Law- To every action there is an equal and opposite reaction.

NEWTON’S 2ND LAW OF

MOTIONBY :

Rohan Karmakar, Jalay Makhwana,Abhishek Lakhani, Amar Junani,

Sonali Jambu, Dishant Jadav

NEWTON’S 2ND LAWS OF MOTION

NEWTON’S SECOND LAW OF MOTION STATAES THAT :

The rate of change of momentum of a body is directly proportional to the

applied unbalanced force in the direction of force

i.e.

Where, dp = change in momentum and dt = time taken for this change.

NEWTON’S 2ND LAWS OF MOTION

A truck at rest does not require any attention. But a moving truck even at low speeds of 5 m/s , may kill a person standing in its path. A small mass, such as bullet may kill a person when fired from a gun.

The observations suggest that the impact produced by the objects depends on their mass and velocity.

NEWTON’S 2ND LAWS OF MOTION

One such property was called Momentum was introduced by Newton.The momentum (p), of an object is product its mass (m) and velocity (v).i.e. p = mvMomentum can be defined as – The quantity of motion possessed by a moving body.

The S.I. unit of Momentum is Kg m s-1

MATHEMATICAL FORMULATION

Consider a body of mass ‘m’ moving with initial velocity ‘u’.Let a Force ‘F’ act on the body for time ‘t’ so that the velocity after time ‘t’ is ‘v’.

Initial momentum of body, p1 = muFinal momentum of body, p2 = mv

M F

u

t = 0

M F

v

t = t

MATHEMATICAL FORMULATION

Now, change in momentum of body = p2 – p1 = mv – mu = m(v-u) Time taken to change this momentum = (t – 0) = t Rate of change of momentum = =

MATHEMATICAL FORMULATION

According to Newton’s 2nd Law of Motion – Force applied rate of change of momentum

Or F ………(i)Since v = u + at OR = aTherefore, eqn. (i) can be written as – F maOr F = kma ……… (ii)Where K is constant of proportionality.

MATHEMATICAL FORMULATION

The value of K can be found as:

F = 1 unit m = 1 unit a = 1 unitThen from eqn. (ii) - 1 = k 1 1 Thus, K = 1And eqn. (ii) becomes - F = ma

2ND LAW OF MOTION IN VECTOR FORM

We know, Force (F) and acceleration (a) are vector quantities, whereas mass (m) is scalar. Therefore, Newton’s 2nd law of motion ca be written in vector form as

F = maThis relation shows that the direction of force applied on the body is same as the acceleration produced in the body.

S.I. UNIT OF FORCEWe know, F = maS.I. unit of mass, m = 1 kgS.I. unit of acceleration, a = 1 ms-2 S.I. unit of Force, = 1 kg ms-21 kg ms-2 is also known as 1 Newton or 1N Also C.G.S. unit of force is, 1 Newton = 105 Dyne

SOME APPLICATIONS

2ND LAW OF MOTION

APPLICATIONSA CRICKET PLAYER LOWERS HIS HANDS WHILE CATCHING THE BALL :

If a player does not lower his hand while catching the ball, the time to stop the ball would be very small. So a large force has to be applied to reduce the velocity of the ball to zero or to change the momentum of ball. When a player lowers his hands, the time to stop the ball is increased and less force has to be applied to cause the same change in momentum of ball. Therefore, the hands of the player are not injured.

APPLICATIONSHUGE DAMAGE TO THE TRAIN TAKES PLACE WHEN IT SUDDENLY COLLIDES WITH A STATIONARY TRAIN :

When a fast moving train suddenly collides against a stationary train, there is large change in the momentum of the moving train. This large change in momentum of train is brought about in short time interval. Hence, a large retarding force acts on the moving train. Due to this large force, huge damage is done to the moving train.

APPLICATIONSA BOXER MOVES HIS HEAD BACKWARD WHEN HIS OPPONENT BLOWS A PUNCH:

When a boxer blows a punch on the face of another boxer, then the change in momentum of punch on striking the face of another player exerts a large force on his face. On the other hand, when the boxer moves his head backward, then the change in momentum takes place in large time interval. Thus, force on the face of boxer becomes less.

?? QUESTIONNAIRE ??1. NAME THE UNIT OF FORCE IN C.G.S. SYSTEM.2. HOW MANY DINES ARE IN ONE NEWTON ?3. WHY VEHICLES ARE FITTED WITH SUSPENSION OR

SPRINGS ?4. WHAT IS UNIT OF MOMENTUM ?5. NAME UNIT OF MOMENTUM IN C.G.S. SYSTEM.6. DEFINE MOMENTUM.7. IS FORCE VECTOR OR SCALAR QUANTITY ?

ALL GOOD THINGSMUST COME TO AN END !

THANKS