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Dr. Homi Bhabha Competition Test Series

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Work,EnergyandSimpleMachine

Work

Work: When an object is displaced by applying force on it , work is said to be done.Example : Walking ,Lifting object, Playing football.

What is work?

We often use the word "work" in our everyday lives. For example, we would say that getting good grades in school takes a lot of hard "work". In physics, the term "work" has a specific meaning.

Work, in physics, occurs when a force acts on an object to move it some distance from the start point (also called displacement). Work is calculated as the force times the distance.

Work = Force * distance or W = F*d

Units of Work

When using SI Units in the work formula, the force is in Newtons, and distance is in meters.

The Joule(J) is the SI unit of work. A Joule is equal to 1 Newton Meter.

Work Done

Sitting and looking at a computer screen is not work. Tapping on the keyboard and making the keys move is work. Your fingers are applying a force and moving the keys. You have to exert a force AND move something to qualify as doing work.

Imagine that you are holding a brick above the ground. Your arm is straight out in front of you and it's pretty tough to hold. Slowly, your arm gets tired, the brick feels heavier and heavier, and you finally have to stop to let your arm rest. Even though you put forth



a lot of effort to hold the brick up, did you do any work on the brick? Nope. The brick didn't move. No work was done if no movement happened. If you lifted the brick again after your arm had rested, that would be work.

Work Not Done

Pushing a wall all day may feel like work, but unless you get that wall moving you're not doing any work according to the rules of physics

Work Depends on Direction

If all of the force acts in the same direction as the motion, all the force does work. If part of the applied force acts in the direction of motion, that part of the force

does work If none of the force is applied in the direction of the motion, the force does no

work.



Energy

Energy It is measured by the amount of work done, usually in joules or watts.Because energy is defined via work, the SI unit for energy is the same as the unit of work – the joule (J),



Different forms of energy:



1. Mechanical energy:

A. Potential Energy B. Kinetic Energy

Potential energy, expressed in science as U , is energy that is stored within an object, not in motion but capable of becoming active. When at rest, every object has rest mass potential energy; if the object is in a position to be affected by gravity and to fall, it has gravitational potential energy. Once an object is in motion, potential energy is converted to kinetic energy , which is the energy of motion.There are a number of kinds of potential energy.

The pendulum of a clock, at the top of its swing, has gravitational potential energy which is converted to kinetic energy as it falls.

Elastic potential energy is present in an object that can be stretched out and rebound, like elastic. The potential energy is stored when an elastic is stretched, and converted to kinetic energy when the elastic is released.

Other types of potential energy include chemical, which is related to the formation of chemical bonds and electrical, expressed as voltage .

2. Chemical Energy: Chemical energy is the energy stored within chemicals, which makes it energy inside atoms and molecules. It is a form of potential energy that you won't observe until a reaction occurs.Chemical energy is also defined as energy that is available for release from chemical reactions.



Example:

coal –combustion reaction converts chemical energy into light and heat wood - combustion reaction converts chemical energy into light and heat petroleum - can be burned to release light and heat or changed into another form of chemical

energy, such as gasoline chemical batteries - store chemical energy to be changed into electricity food - digested to convert chemical energy into other forms of energy used by cells

3. Electrical Energy:

The flow of electricity is a form of Kinetic Energy.

4. Light Energy: Light energy is the only form of energy that we can actually see directly. It is formed through chemical, radiation, and mechanical means. Light energy can also be converted into other forms of energy.

5. Sound Energy: Sound energy is a form of energy that is associated with vibrations of matter. It is a type of mechanical wave which means it requires an object to travel through. This object includes air and water. Sound originates from the vibrations that result after an object applies a force to another object.



Example: vibrating drum, vehicles drivingflushing, water from your shower, the sound of me slapping my forehead after reading this question

6. Magnetic Energy : Magnetic energy is the energy within a magnetic field.energy results in various metals either repelling or attracting each other

Examples: MRI machine, Magnetic Compass,

7. Nuclear Energy: At a basic level, nuclear power is the practice of splitting atoms to boil water, turn turbines, and generate electricity.the energy released during nuclear fission or fusion, especially when used to generate electricity.Nuclear power comes from the process of nuclear fission, or the splitting of atoms. The resulting controlled nuclear chain reaction produce steam, and drive turbines that generate electricity.

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Example: vibrating drum, vehicles driving by, noisy neighbors, radio, music player, toilet flushing, water from your shower, the sound of me slapping my forehead after reading

Magnetic energy is the energy within a magnetic field.various metals either repelling or attracting each other

MRI machine, Magnetic Compass, Hard disks, Door of Fridge

At a basic level, nuclear power is the practice of splitting atoms to generate electricity.

the energy released during nuclear fission or fusion, especially when used to generate

Nuclear power comes from the process of nuclear fission, or the splitting of atoms. The resulting controlled nuclear chain reaction creates heat, which is used to boil water, produce steam, and drive turbines that generate electricity.

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by, noisy neighbors, radio, music player, toilet flushing, water from your shower, the sound of me slapping my forehead after reading

Magnetic energy is the energy within a magnetic field. This

Hard disks, Door of Fridge

At a basic level, nuclear power is the practice of splitting atoms to

the energy released during nuclear fission or fusion, especially when used to generate

Nuclear power comes from the process of nuclear fission, or the splitting of atoms. The creates heat, which is used to boil water,



Source of Energy

1. Conventional or non renewable : coal , fossil fuel , petrol ,diesel and natural gas.

2. Non conventional or renewablea. Solar energyb. Wind energyc. Tidal energyd. Hydroelectric energye. Ocean wavesf. Atomic energy

Principle of Conservation Of Energy

Energy can neither be created nor destroyed; rather, it transforms from one form to another.



Simple Machine



Lever

A lever is a simple machine and can be moved to move a load (or does work). Effort is applied to one part of the lever and it pushes the load at another part. It consists of Load, Effort and Fulcrum. Fulcrum is the the point or support on which a lever turns. Effort is the point where the force is applied on the load.

Load Arm Distance between Load and FulcrumEffort Arm Distance between Effort and Fulcrum

Types of Lever (Remember word FLE.)

First Order Lever F is in between load and effortExample: Crow- bar ,see-saw, and spoon used to open the lid of can,the handle of pump, a pair of scissors, a common balance, a nail extractor, beam

balance, a broom

Second Order Lever L is in between F and EExample: The bottle opener ,the wheelbarrow ,nut cracker, Lemons squeezer, Can Opener Third Order Lever E is in between L and F

Example: Forceps ,the human arm, a pair of tongs ,a knife ,fishing rod

First Order Lever E---F ---L 1.Crow Bar 2.Pliers

See- Saw Scissor

Second Order Lever E---L---F Wheel Barrow Nut Cracker

Bottle Opener Vegetable Cutter

Third Order Lever L---E ---F Human arm Tongs

Fishing rod

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