Presented by :-

•Muhammad Usman Zafar 11-MC-11•Faheem Fiaz 11-MC-17•Ahsan Mahmood 11-MC-27

• Muhammad Usman Zafar

11-MC-11

OverviewOf

Presentation

Energy Energy is an indirectly observed quantity that

is often understood as the ability of a physical system to do work on other physical systems. Energy came from the Greek word “energeia” meaning “activity or operation.” It was used in one of Aristotle’s works in as early as the 4th century BC.

Work• In physics, mechanical work is a

scalar quantity that can be described as the product of a force and the distance through which it acts in the direction of the force. The term work was first coined in 1826 by the French mathematician Gaspard-Gustave Coriolis.

• If a constant force of magnitude F acts on a point that moves a distance d in the direction of the force, then the work W done by this force is calculated as

W=F.d W= work done F= force d= displacement in the direction of the

force

• For example, if a force of 10 newton (F = 10 N) acts along point that travels 2 meters (d = 2 m), then it does the work W = (10 N)(2 m) = 20 N m = 20 J.

Basic Concept

• Energy is the ability to do work. However, to understand energy we must understand what scientists mean by “work.” It might seem that it is work to try to solve a problem or to stand at attention for 15 minutes. But that is not “work” to a scientist. In science, work is motion against resistance. Lifting a box against the pull of gravity is work, as is driving a nail into a board against the friction of the wood or winding a clock against the resistance of the spring.

• In doing this work (or any other kind), energy is used up. Both work and energy are measured according to the distance an object is moved and the force that must be overcome to keep the object moving. Suppose a pound of iron is lifted 1 foot. Then 1 foot-pound of work has been performed and 1 foot-pound of energy has been used up.

• We need energy to do any kind of work. If someone says that he does not have the energy required to do the job, he is merely reiterating this work energy relationship. Energy is like currency in hand which you use for shopping. Greater the energy you have, more is the amount of work you can perform.

Summary• Energy is the ability to produce or create

work. Work, on the other hand, is the ability to provide force and a change in distance to an object.

• There are many types of energy such as solar energy, etc., but there is only one type of work.

• Energy was coined since 4 BC while work was only used in 1826.

• Both work and energy are scalar units.

• Both work and energy are measured in joules.• Work is transfer of energy• Work is done on an object when you transfer

energy to that object• The change in the kinetic energy of an object

is the net work done on it• The rate of doing work is same as that of

consuming energy

Faheem Fiaz11-MC-17

What is ENERGY?

• The ability of a body to do

work.

• Energy is useful to mankind.

Electrical

Chemical

Nuclear

Magnetic

Sound

Mechanical

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Chemical energy is the energy stored in the bonds of atoms and molecules. This a form of potential energy until the bonds are broken. Fossil fuels and biomass store chemical energy. Products that contain chemical energy include: TNT, baking soda, and a match. Biomass, petroleum, natural gas, propane and coal are examples of stored chemical energy.

Forms of Energy

Electrical energy is the movement of electrons. Lightning and static electricity are examples of electrical energy that occur naturally. Science hasn't found a way to use natural forms of electrical energy, like lightning. Instead, we use different energy sources to create electrical energy by using generators and turbines.

Forms of Energy

Nuclear energy is the energy stored in the nucleus of an atom. Nuclear energy is unusual in that it can give off energy in the form of light or heat. Submarines, power plants, and smoke detectors all use nuclear energy. Nuclear power plants use uranium, a radioactive element, to create electricity.

Forms of Energy

Sound energy is the movement of molecules in the air that produces vibrations. Alarms, music, speech, ultrasound medical equipment all use sound energy. VCR tapes change sound energy into electrical energy. The electrical energy records the sound using magnetic tape. Speakers read the magnetic tape and change it back into sound. Forms of

Energy

Mechanical energy is the movement of machine parts. Mechanical energy is also the total amount of kinetic and potential energy in a system. Wind-up toys, mechanical machines are examples of mechanical energy. Wind power uses mechanical energy to help create electricity.

Potential energy + Kinetic energy =

Mechanical energy

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Magnetic energy is the attraction of objects made of iron. Medical equipment, compass, refrigerator magnets are all examples of magnetic energy. Any type of energy source that uses a generator in the process to make electricity uses magnetic energy.

Forms of Energy

• Kinetic Energy: Everything you see moving about has kinetic energy.  The kinetic energy of an object in this case is given by the relation:

• KE = (1/2)mv2

• Potential energy : Potential energy exists whenever an object which has mass has a position within a force field. The most everyday example of this is the position of objects in the earth's gravitational field. The potential energy of an object in this case is given by the relation:

• PE = mgh

Ahsan MahmoodAhsan Mahmood11-MC-2711-MC-27

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Work is the transfer of energy through motion. In order for work to take place, a force must be exerted through a distance. The amount of work done depends on two things: the amount of force exerted and the distance over which the force is applied. There are two factors to keep in mind when deciding when work is being done: something has to move and the motion must be in the direction of the applied force. Work can be calculated by using the following formula: Work=force x distance

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Work is done on the books when they are being lifted, but no work is done on them when they are being held or carried horizontally.

• Work is done……by a force when the

object it acts on moves

NO work is done by pushing against a stationary wall.

•Work IS done throwing a ball because the ball MOVES while being pushed during the throw.

Product of the applied force and the displacement of an object in the direction of the applied force

W=F.s

W = work doneF = forces = displacement in the direction of the

force

Examples • If a box is pushed with a force of 40 N

and is moves steadily through a distance of 3 m in the direction of the force, calculate the work done.

Solution: F= 40 N

s = 3 m

Work done, W = Fs = 40N x 3m =120J

• A woman pulls a suitcase with a force of 25 N at an angle of 60o with the horizontal. What is the work done by the woman if the suitcase moves a distance of 8 m along the floor.

• Solution: F = 25 N

s = 8 m

W = 25 cos 600 x 8 = 100 J60o

Relationship of work and energy

When we lift an object (this book, for example) from one level to another (say,from the floor to a shelf on the wall), we expend our energy – by doing work – to increasethe energy stored in the object. (This energy can be converted back into work, for example,if we let the book fall back to the floor.) In this transformation, the chemical energy storedin our muscles is converted to work, or more precisely to mechanical energy, and work isconverted into the potential energy stored in the object (while it sits on the shelf).

Direction of Force

• When a force and the distance through which it acts are parallel, the work done is equal to the product of F and d

• If the forces are NOT parallel, work done is equal to the product of d and the projection of F in the direction of d.

Difference between Work and Energy

Work Energy

Work is the transferring of an energy’s amount via a force through a distance via the direction of the force.

Energy is all defined as the ability to push or pull by exertion in a certain path or distance.

A block displaced along a table by force (F) and distance (D)

Examples of energy are nuclear energy, solar energy, electrical energy, and a lot more.

It is mathematically given as W=F.d

It is either given as K.E= 1/2mv² or P.E=mgh