Energy

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ENERGY

K Warne

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Energy

• Write down a definition that explains what energy is.

The ability to do work.

• Write down as many forms of energy as you can. Energy can

be…

Chemical, movement (kinetic), electrical, solar, nuclear, potential

(stored), radiant, light, sound, hydro-electric

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Forms of Energy

Form of Energy Source/Origin Transferred

into/Used

Process/

Transducer

Solar Sun Heat/Electricity

Chemical

Solar panels

photosynthesis

Wind Wind - Sun Electricity/

Identify as many different forms of energy as you can, try and decide

where the energy comes from (source), where it goes to (Transferred

into...) and where this takes place (process/transducer).

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NUCLEAR ENERGY

Is the process in which the

nucleus of heavy

(radioactive) elements are

split apart.

This releases a lot of energy.

The process in which small

nuclei are joined together

(fused) to form larger nuclei.

This releases VAST

QUANTITIES of energy.

Both these forms of energy can be used to provide the energy we

need. Find out why they are both called “Nuclear”, how are they

different? Give an examples of both.

H H

He

FUSIONFISSION

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Origins of Energy - The Sun

• Energy can never be created or destroyed.

• It can only be transformed from one form to another.

• Energy from the sun (solar - heat/light

energy)

• Enables plants to grow (photosynthesis)

• Which can be harvested /eaten (food/fuel -

chemical energy)

• used to do work (heat/light energy)

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Potential Energy Gravitational

m Any object that is above the ground has the

POTENTIAL to fall Down.

It has potential energy (EP) - given by:

Ep = mghwhere;

m = the mass of the object (kg)

g = the acceleration due to gravity (10m/s2)

h = height above the ground (m)

If the object is lifted up then it gains the

same amount of potential energy again.

g(10m/s2)

EK Potential

Energy (mgh)

m

m

Ep Potential

Energy GAINED

Object could fall down

h

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Mechanical Energy - Falling Object

m Any object that is above the

ground has the POTENTIAL to

fall Down.

The potential energy EP =mgh

(Height) lost would be converted

into speed (kinetic energy) EK.

Ep(Top) = Ek(Bottom)

If the object is lifted up then it

gains potential energy.

At any time the sum of these two

is called the MECHANICAL

ENERGY - and it stays constant.

Ep Potential

Energy LOST

EK kinetic energy

gained = Ep lost!

E = Ep + Ekm

4kg

8m

Ep = mgh

Ek = 320J

E = Ep + Ek

= 320 + 0

= 320J

E = Ep + Ek

= 0 + 320

= 320J

4mE = Ep + Ek

= 160 + 160

= 320J

Ep = 0

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Mechanical Energy - Falling Object

m Any object that is above the

ground has the POTENTIAL to

fall Down.

The potential energy EP =mgh

(Height) lost would be converted

into speed (kinetic energy) EK.

Ep(Top) = Ek(Bottom)

If the object is lifted up then it

gains potential energy.

At any time the sum of these two

is called the MECHANICAL

ENERGY - and it stays constant.

Ep Potential

Energy LOST

EK kinetic energy

gained = Ep lost!

E = Ep + Ekm

4kg

8m

Ep = 320J

Ek = ??

320J

E = Ep + Ek

= 320 + 0

= 320J

E = Ep + Ek

= 0 + 320

= 320J

4mE = Ep + Ek

= 160 + 160

= 320J

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A pendulum

• A person of 60kg is lifted to a height of 30m on a slingshot

pendulum and then released.

m

h

ETop = Ep + EK

= mgh + 1/2mv2

= (60)(10)(30) + 0

= 18000J

Total Mechanical Energy

(Top)

EBottom = Ep + Ek

= mgh + 1/2mv2

18 000 = 0 + 1/2 (60)v2

v2 = 18000/30 = 600

v = 600 = 24.5 m.s-1

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Kinetic & Potential Energy Tasks

1. Calculate the potential energygained by your body as you climb the stairs to the first floor of the school building.

2. Calculate the potential energygained by a cricket ball 300g that is thrown 4m up into the air.

3. Calculate the potential energygained by your bag (weigh it) as it is lifted onto your shoulder(estimate or measure height).

4. Calculate the kinetic energy of your body as you are;

4.1 walking (1.5m.s-1)

4.2 running (8m.s-1)

4.3 driving in a car (60km.h-1).

5. Calculate the mechanical energyof a 2 ton airplane flying at a height of 30 000m at a speed of 500 km.hr-1.

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Energy Transformations

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Energy Transformations

A car accelerates from rest to 120km/hr and then

comes to a halt again. List the energy

transformations that take place.

Chemical Potential energy - in the petrol.

Heat energy in the engine as the petrol

burns.

Kinetic energy as the engine and car begin

to move.

All this energy is converted into heat as the

car brakes and comes to a halt.

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Energy Efficiency - Light Bulb

• Input: Electrical

• Outputs: Heat & Light

• Page 108 - analysis of

energy input and outputs for

a light bulb

• Transfer these to a pie chart.

(Outputs only)

• Energy Spreadsheet

Electrical

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Temperature

•Temperature is a measure of the average kinetic energy of the particles in a substance.

•The HOTTER the substance the GREATER the KINETIC ENERGY and the FASTER the particles vibrate.

Heat

• HEAT is the ENERGY which passes from a HOT object to a COLD object.

• HEAT is ENERGY on the MOVE!

Heat is transferred by:

• Conduction

• Convection

• Radiation

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Heat - energy on the move

1. Radiation - Infra red radiation - rays of heat

energy that move in straight lines through

space.

2. Convection - movement of heat energy in

a current of liquid or gas. Hot air rises

(less dense) causes convection currents.

3. Conduction - Heat transmitted through a

substance or from one substance/object to

another by direct contact.

H/W: Draw a diagram/picture showing how

each of these operates in a example.

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Heat - preventing heat loss.

Write down ways that energy losses in a house can be

prevented.

Ceiling insulation

- Aerolite

Cavity wall (insulation)

Carpets - underfloor heating

Windows

- curtains

- draft

excluders

- double

glazing

Doors -

draft

excluders

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Energy

• Chemical energy in the

petrol.

• Converted to kinetic energy

in the engine which moves

the car.

• Converted to HEAT in the

brakes.

Discuss the energy transformations that occur when a car

drives a certian distance and then stops.

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Hi -

This is a SAMPLE presentation only.

My FULL presentations, which contain loads more slides (with all the gaps filled in) as well as

other resources, are freely available on my resource sharing website:

www.warnescience.net

(paste into your browser if link above does not work)

Have a look and enjoy!

Keith Warne