Lesson 2- Do now! 1 Energy Types Word Scramble 2 Title – Energy Flow diagrams and the date.

Lesson 2- Do now!1 Energy Types Word

Scramble

2 Title – Energy Flow diagrams and the date

Some examples of forms of energyKinetic energy (KE)Energy due to a body’s motion.

Potential energy (PE)Energy due to a body’s position

Thermal energy Energy due to a body’s temperature.

Chemical energyEnergy associated with chemical reactions.

Nuclear energyEnergy associated with nuclear reactions.

Electrical energyEnergy associated with electric charges.

Elastic energyEnergy stored in an object when it is stretched or compressed.

All of the above forms of energy (and others) can ultimately be considered to be variations of kinetic or potential energy.

Learning Today

• Energy flow diagrams

• Energy flow circus

• Sankey diagrams

• Potential Energy – P.E.

• Homework Potential Energy Sheet

Other energy measurement examples

4200 joules (4.2 kJ) 1 food Calorie

1 000 000 J (1 MJ) Energy of a Mars bar

0.000 02 J Energy need to produce a syllable of a word

15 000 000 000 000

000 000 000 J

Energy received by the Earth from the Sun in one day

Conservation of energyEnergy cannot be created or destroyed. It can only be transformed from one form to another form.

Conservation of energy also means that the total energy in the universe stays constant.

Energy Flow diagrams – Copy please

Energy flow diagrams show energy transformations.

Work done = energy transformed For example, when a car brakes, its kinetic energy is

transformed into heat energy in the brakes.

Kinetic heat

19/04/23

Energy changesEnergy changes

To describe an energy change for a light bulb we need to do 3 steps:

Electricity Light + heat

1) Write down the starting energy:

3) Write down what energy types are given out:

2) Draw an arrow

Draw energy flow diagrams for the following…?

1) An electric fire

2) A rock about to drop

3) An arrow about to be fired

Television

electrical

light

sound

heat

What are the main energy transfers for a television (don’t forget the wasted energy)?

Car engine

chemical

kinetic

sound

heat

What are the main energy transfers for a car engine (don’t forget the wasted energy)?

Radio

electrical

sound

heat

What are the main energy transfers for a radio (don’t forget the wasted energy)?

Pendulum oscillation

GRAVITATIOINAL POTENTIAL ENERGY

KINETIC ENERGYMAXIMU

M

MINIMUM

MAXIMUM

ZERO

The total energy, gravitational potential plus kinetic, remains the same if there are no significant resistive forces

Wasted sound energy

Can you name some devices that waste energy as sound?

_____________

_____________

_____________

_____________

_____________

_____________

_____________

_____________

Hairdryer

Washing machine

Car engine

Computer

Microwave

Bunsen burner

Wind turbine

Dish washer

Wasted heat energy

Can you name some devices that waste energy as heat?

_____________

_____________

_____________

_____________

_____________

_____________

_____________

_____________

Computer

Turbine

Motor

Transformer

Any electrical device

Television

Radio

Car engine

What happens to wasted energy?

Wasted e_____ spreads out (d_______) into the s_________.

This makes the energy harder to r____.

Remember energy can not be c______ or d_______.

What happens to the wasted energy you get whenever energy is changed from one form to another?

This is why it is important to r_____ the amount of wasted energy there is.

reated estroyed

nergy issipatedurroundings

e-use

educe

Choose appropriate words to fill in the gaps below:

Energy is required to do ________.

Energy is measured in ________ (J)

Energy cannot be created or ___________ but can only change ________.

Kinetic energy is the energy possessed by __________ bodies.

When an object is lifted up it gains gravitational _____________ energy.

Heat or __________ energy is often produced as a _________ energy form, dissipated to the surroundings.

workformmoving joulespotential thermal destroyed

WORD SELECTION:

wasted

work

form

moving

joules

potential

thermal

destroyed

wasted

Lesson 3 Do Now How much

energy sort, please

arrange the statements in order of how much energy is involved .

• Energy to drive a car 60 miles: 250,000,000 J

• Energy stored in 1 litre of petrol: 34,000,000 J • Energy used by the human body for 1 day: 10,000,000

J• Energy in a typical chocolate bar: 1,000,000 J• Energy to boil 1 l of water, from freezing: 500,000 J• Energy stored in a peanut: 25,000 J• Kinetic energy of a fast-moving cricket ball: 1000 J• Energy stored in one new AA battery: 1000 J• Energy from burning one whole match: 1000 J• Energy to lift up an apple by one metre: 1 J• Energy to lift up 1N by one metre: 1 J• Energy to make the human heart beat once: ½ J• Energy to press key on computer keyboard: 1/100 J

Learning Today• Potential Energy – Ep.

• Homework Potential Energy Sheet due Thursday 12th January 2012

• Kinetic Energy – Ek

• If you need to find me, I will usually be in my classroom SS15 or the science office SS3

• Next lesson I want to spend half the lesson building roller-coaster, you need your log on details.

Potential Energy – Copy this

m h

P.E.

gP.E.= gravitational potential energy J m = mass kgg = gravitational field strength = 10 N/kgh = height m

Now make mass, gravitational field strength and height the subject of the formulae

mghEP ..GPE = mass x height x Change in

height

Gravitational potential energy is the energy an object has because of its position in a gravitational field

Rearranging the formulae

m h

P.E

g

mghEP ..

mghEp

gh

Em p

mh

Eg p

Ep= gravitational potential energy (J)

m = mass (kg)g = gravitational field strength (Nkg-1)h = height (m)

mg

Eh p

m h

Ep

g

Example

A dog of mass 12 kg falls from an aeroplane at a height of 3.4 km. How much gravitational energy does the dog have as it leaves the aeroplane?

Woof! (help!)

ExampleOn earth g = 10 m/s2

Height = 3.4 km = 3400 m

Mass of dog = 12 kg

ExampleOn earth g = 10 m/s2

Height = 3.4 km = 3400 m

Mass of dog = 12 kg

GPE of dog = mgh = 12 x 10 x 3400 = 408 000 J

Example

GPE of dog = mgh = 12 x 10 x 3400 = 408 000 J

Just before the dog hits the ground, what has this

GPE turned into?

Example

GPE of dog = mgh = 12 x 10 x 3400 = 408 000 J

KE at bottom = 408 000 J

Just before the dog hits the ground, what has this GPE turned into? Kinetic energy

What type of energy is stored in a coiled spring?

A. Sound

B. Kinetic

C. Elastic

D. Gravitational

What type of energy is stored in baked beans?

A. Sound

B. Gravitational

C. Chemical

D. Elastic

What is the change in gravitational potential energy of a weight of 60N that moves through a distance of 6m?

A. 10J

B. 360J

C. 66J

D. 54J

What is the kinetic energy of a ball of mass 6kg and velocity 5ms-1?

A. 75J

B. 30J

C. 1.2J

D. 150J

What type of energy is stored in coal, oil and natural gas?

A. Light

B. Heat

C. Sound

D. Chemical

Kinetic energy

19/04/23Some example questions…Some example questions…How much gravitational potential energy have the following

objects gained?:

1. A brick that 10 kg lifted to the top of a house 10m

2. A 1000kg car lifted by a ramp up to a height of 50cm,

3. A 70kg person lifted up 50m by a ski lift. How much GPE have the following objects lost?:

4. A 0.2 kg football dropping out of the air after being kicked up 30m,

5. A 0.5N egg falling 10m out of a bird nest,

6. A 1000kg car falling off its 50cm ramp.

7. Mr Richards when bungi-jumping off a 110-metre high bridge in Zambia in August

Learning today Learning today

•how to use the K.E equation.

•K.E. and G.P.E problems

© Boardworks Ltd 2003

Kinetic energy

This is the energy possessed by an object due to its movement.

What factors will increase the amount of kinetic energy a moving object has?

The velocity of the object

The shape of the object

The mass of the object

The height of the object

x

x


Lesson 4 Kinetic Energy

Do Now Work Done questions

p79 Q1,2&3

I will collect books today I will collect books today Learning today Learning today

1. how to use the K.E equation.

2. K.E. and G.P.E problems

Or with good behaviour and good work

2. Build a roller-coaster in the computer room

2

2

1. mvEK

2

2

v

Em k

m

Ev k2

½ v2

K.E.

mK.E. = kinetic energy Jm = mass kgv = speed m/s

Kinetic Energy

2

2

1. mvEK

2

2

v

Em k

m

Ev k2

½ v2

K.E

m

Ek = kinetic energy Jm = mass kgv = speed m/s

Kinetic Energy Now make mass and velocity the subject of the equation

2

2

1. mvEK

2

2

v

Em k

m

Ev k2

K.E. = kinetic energy Jm = mass kgv = speed m/s

Kinetic Energy

Copy This increase the mass you increase the kinetic energy.

double the mass you double the K.E.

increase the speed you increase the K.E.

double the speed you ? the K.E.


Kinetic energy calculation Copy this

Kinetic energy =

=

=

A car has a mass of 400kg and a velocity of 10 ms-1, what is the kinetic energy of the car?

ExampleA bullet of mass 150 g is travelling at 400 m/s. How much kinetic energy does it have?

Example

A bullet of mass 150 g is travelling at 400 m/s. How much kinetic energy does it have?

K.E. = mv2/2 = (0.15 x (400)2)/2 = 12 000 J

Let’s try some questions!

• Homer Simpson Skateboarding

Homer PE to KE.mpg

Stick them in first!

Lesson 5 Do NowBobsleighing Work

done sheet

4. pencil case containing pen, pencil, ruler & eraser

• Wait quietly outside the lab at the start of the lesson

• Be prepared to learn, have your

1. textbook

2. exercise book

3. calculator

How to make Ms Cornish happy

Learning today Learning today 1. Calculate velocity from

the K.E. equation.

2. K.E. and G.P.E problems

3. Q 8 & 9 from G.P.E. homework

How to find speed

2..

2mvEK

• A hot air balloon of mass 250kg at a height of 150m descends slowly into a field.

• Work out the P.E. before descent

• What happens to the P.E. as a result of its descent?

• If the balloon burst at a height of 150m, what would be its speed of impact on the ground?

K.E. Q 7

Example

GPE of dog = mgh = 12 x 10 x 3400 = 408 000 J



Example

GPE of dog = mgh = 12 x 10 x 3400 = 408 000 J

KE at bottom = G.P.E


Example

K.E.= P.E

K.E.= 408 000J


2..

2mvEK

Example

Assuming no energy is lost as air resistance – in reality the dog would have reached

TERMINAL VELOCITY

Lesson 6 Do Now Q3 & 4 page 83

Top Gear Bobsleighing

I will collect books today I will collect books today Learning today Learning today

1. How to remember the G.P.E & K.E equation.

2. % Efficiency

3. Power

To remember equations Gravitation Potential Energy P.E.

G.P.E. = massive great heightmghEP ..

To remember equations

Movement Energy K.E.

K.E. = move up 2 down 2

K.E Brainpop2

..2mv

EK

Power - Copy this

P t

E

P = Power W E = energy transferred J Wd = work done Jt = time taken s

Unit Watts – W Joules /second – J/s

t

EP

Power = Energy transfer

time taken

Power is the rate of energy transfer or rate of work done unit is the Watt - W

t

WdP

Power Example

• If a engine does 1000 joules o f useful work in 2 seconds

t

WdP

Sankey Diagram

A Sankey diagram helps to show how much light and heat energy is produced

Sankey Diagram

The thickness of each arrow is drawn to scale to show the amount of energy

Sankey Diagram

Notice that the total amount of energy before is equal to the total amount of energy after (conservation of energy)

Efficiency

Although the total energy out is the same, not all of it is useful.

Efficiency

Efficiency is defined as

Efficiency (%) = useful energy output x 100

total energy input

Efficiency

Efficiency is defined as

Efficiency (%) = useful energy output x 100

total energy input

Can you copy this (with title) please?

Example

Efficiency = 75 x 100 = 15%

500

Energy efficient light bulb


100

Energy efficient light bulb


100 That’s much better!

Energy efficient light bulbs• These produce more useful light

energy for the same amount of input electrical energy.

• They waste less energy to heat.

More complex examples

Here is a more complex energy transformation Here is a more complex energy transformation diagram, the sort used by engineers. diagram, the sort used by engineers. This one is for an aeroplane engine.This one is for an aeroplane engine.

19/04/23

Question 1

Calculate the efficiency of an electric motor if it produces 48J of useful kinetic energy when supplied with 80J of electrical energy.

efficiency = useful energy output

total energy input

efficiency = 48J 80J

efficiency of the motor = 60%

x 100%

x 100%

Question 2

Calculate the useful light output of a light bulb of efficiency 20 % when it is of an electric motor if it supplied with 400J of electrical energy.

20 = useful energy ÷ 400J

useful energy = (20 x 400J)/100

light output = 80J

efficiency = useful energy output

total energy inputx 100%

Improving efficiency – Please copy

Decrease loss to heat by:Reducing friction by using a lubricant (eg oil).

Reducing electrical resistance in electrical circuits.

Reducing air resistance by using streamlined shapes.

Reduce loss to sound by tightening the loose parts of machinery.

Let’s try some questions!

Stick the sheet into your books and answer the questions in your

books please

Ready?Good Luck

today!

Energy Circus

Around the room are a few examples of energy changes (some simple, some a little more complicated!)

For each example I want you to write the name of the experiment and then the energy flow diagram for that experimentYou will have 2 minutes on each example.

Lesson 2- Do now! 1 Energy Types Word Scramble 2 Title – Energy Flow diagrams and the date.

Documents

Transcript of Lesson 2- Do now! 1 Energy Types Word Scramble 2 Title – Energy Flow diagrams and the date.