PHYSICS ICT PRESENTATION

GROUP MEMBERS – SHUBHAM SHARMA [35]POONAM LODHA[25]KUNDAN KHUDKHUDE[17]SAMIKSHA MUNDADA[30]YASH WADAJKAR[42]

TOPIC – FORCE AND LAWS OF MOTION

Sir Isaac Newton PRS (/ˈnjuːtən/;[6] 25 December

1642 – 20 March 1726/27[1]) was an English physicist and mathematician(described in his own day as a "natural philosopher") who is widely recognised as one of the most influential scientists of all time and a key figure in the scientific revolution. His book Philosophiæ Naturalis Principia Mathematica ("Mathematical Principles of Natural Philosophy"), first published in 1687, laid the foundations for classical mechanics. Newton made seminal contributions to optics, and he shares credit with Gottfried Wilhelm Leibniz for the development of calculus.

Newton's Principia formulated the laws of motion and universal gravitation, which dominated scientists' view of the physical universe for the next three centuries.

SIR ISAC NEWTON

WHAT IS FORCE?

0 Any action which causes pull , hit , or push on a body is called force. Force is used in our everyday actions like pushing , pulling , lifting , stretching , twisting and pressing. Force cannot be seen but it can be judged only by the effects which it produces in various bodies around us.

EFFECTS OF FORCE

A force can move a stationary object. A force can stop a moving body. A force can change direction and speed of a moving

body. A force can change shape and size of a body.

TYPES OF FORCESBalanced force- When the net effect produced by a number of forces on a body is zero , the forces are said to be BALANCED FORCE . Balanced force can only bring change in shape of a body . An object moves with uniform velocity when the forces acting on object are BALANCED and there is no external force working on it . Balanced force do not change the following functions :

The state of rest .

The state of motion .

2. UNBALANCED FORCE - When the net effect produced by number of forces on a body is non-zero , the forces are said to be UNBALANCED FORCE . The unbalanced force causes a change in the state of rest or of uniform motion . If a unbalanced force is applied on a moving object , there will be a change either in its speed or in the direction of motion . Thus , to accelarate the motion of an object , an unbalanced force is required .

We can also state that the UNBALANCED FORCE is opposite of BALANCED FORCE and BALANCED FORCE is opposite of UNBALANCED FORCE .

Newton ‘s first law describes the behaviour of such bodies which are in a state of rest or of uniform motion in a straight line .

It states that an object will continue to remain at rest or in a uniform motion along a straight line or path unless an external force acts on it . This means all objects resist in changing their state . The state of any object can be changed by applying external force only .

Newton's First Law of Motion:

APPLICATIONS OF Newton's First Law of Motion:

A person standing in a bus falls backward when the bus is started moving suddenly.

A person standing in a bus falls forward when the bus stops suddenly. When the pile of coins on the carom board hit by a striker , coin only at

the bottom moves away leaving rest of pile as it is . The head of hammer is tightened on a wooden handle by banging the

handle against a hard surface.

INERTIA AND MASS

• The tendency of a body to oppose or resist any change in its state of rest or a uniform motion is called INERTIA OF THE BODY .

• It is the inherit property of all the objects . The Newton ‘s first law of motion is also known as the Galileo ‘ s law of inertia . Inertia is directly proportional to to the mass .

• This means that INERTIA increases with increase in mass and decreases with decrease in mass . A heavy object will have more INERTIA than the lighter one.

TYPES OF INERTIA O Inertia is of three types –i. Inertia of rest – The tendency of a body to

oppose any change in its state of rest is known as inertia of rest .

ii. Inertia of motion – The tendency of a body to oppose any change in its uniform motion is known as inertia of motion .

iii. Inertia of direction – The tendency of a body to oppose any change in its direction of motion is known as inertia of direction .

Momentum measures the quantity of motion

possessed by a body . It is defined as the product of mass and velocity of the body . Besides magnitude , it also has a direction . At any instant , its direction is same as the direction of the velocity . Thus , momentum is a vector quantity . If a body of mass m moves with a velocity v , then momentum p = mv . The S.I unit of momentum is kg-m/s . In CGS system , its unit is g-cm/s.

MOMENTUM

Newton's Second Law of Motion:• When two bodies, a heavy one and a light one, are acted

upon by the same force for the same time, the light body attains a higher velocity (or higher speed ) than the heavy one. But the momentum gained by both the bodies is same . The link between force and momentum is expressed in Newton's Second Law of Motion .

• The second law of motion states that the rate of change of momentum of an object is proportional to the applied external force and take place in direction in which external force act

DERIVATING NEWTON ‘ S SECOND LAW OF MOTION

• If a body of mass m moving at initial velocity u accelerates uniformly with an acceleration a for time t so that its final velocity changes to v , then

Initial momentum, p1=mu Final momentum, p2= mvTherefore, Change in momentum = p2 – p1 = mv-mu =m[v-u]According to NEWTON ‘ S SECOND LAW OF MOTION , F = K [Change in momentum/ time] F = K [p2 – p1 / t] F = K [mv-mu/ t] F = K [m[v-u]/ t] [ SINCE , v-u/ t = a ] F = K [m.a]

APPLICATIONS OF NEWTON ‘ S SECOND LAW OF MOTIONA cricket player or a fielder moves

his hand backwards on catching a fast cricket ball

During athletics meet , a high jumping athlete is provided either a cushion or a heap of sand on the ground to fall upon.

IMPULSE Impulse is termed as total impact of force.

This is equal to the change in momentum of body. In other words, impulse is defined as the product of force and a small time in which a force acts.

IMPULSE = CHANGE IN MOMEMTUM It is easily noticable that greater the time of

change in momentum, less is the impact of force.

Impulse is a vector quantity and its direction is same as the direction of force. The SI unit of impulse is N-s or kg-m/s.

Impulse applied to an object in a given time interval can also be calculated from the area under force-time (F-t) cure.

Third law of motion When one body influences another body by

applying force , we say that the first body is interacting with the second body . In any interaction between two bodies , there are always two forces that come into play . And newton ‘s third law of motion describes the relationship between the forces that come into play when the two bodies interact with one another .

According to newton ‘s third law of motion : whenever one body exerts a force on another body , the second body exerts an equal and opposite force on the first body . The force exerted by the first body is known as action and the force exerted by the second body is known as reaction . It should be noted that action and reaction are just forces . We can also say to every action there is equal and opposite reaction.

In the football match , the footballer is kicking the ball with a greater force and collides with a player of the opposite player . Both feel hurt because each applies a force to the other .

During the swimming , a swimmer pushes the water backwards with his hand and leg . The water exerts an equal and opposite push on the swimmer ‘ s body which makes the swimmer move forward .

A fireman has to hold the hose pipe strongly while directing a powerful stream of water on the fire . This is due to the reaction force of stream of water rushing out at a high speed .

The rapid burning of fuel in rocket produces hot gases which rush through nozzle at a very high speed which has its reaction by moving of rocket upwards at a great speed .

APPLICATIONS OF NEWTON ‘ S THIRD LAW OF MOTION

LAW OF CONSERVATION OF MOTIONLaw of conservation of momentum

is a result of newton ‘ third law of motion . According to this law , the total momentum of a system of objects remains conserved before and after their interaction .

THANK YOU !