Do now 1 Energy Types Word Scramble 2

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

Some examples of forms of energy Kinetic energy (KE) Nuclear energy Energy due to a body’s motion. Energy associated with nuclear reactions. Potential energy (PE) Energy due to a body’s position Electrical energy Thermal energy Energy associated with electric charges. Energy due to a body’s temperature. Chemical energy Energy associated with chemical reactions. Elastic energy Energy 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 k. J) 1 food Calorie 1 000 J (1 MJ) Energy of a Mars bar 0. 000 02 J Energy need to produce a syllable of a word 15 000 000 Energy received by the Earth from the Sun in one day 000 000 J

Conservation of energy Energy 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

Energy changes 3/15/2018 To describe an energy change for a light bulb we need to do 3 steps: 1) Write down the starting energy: 3) Write down what energy types are given out: 2) Draw an arrow Electricity Light + heat 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 What are the main energy transfers for a television (don’t forget the wasted energy)? light electrical sound heat

Car engine What are the main energy transfers for a car engine (don’t forget the wasted energy)? kinetic chemical sound heat

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

Pendulum oscillation GRAVITATIOINAL POTENTIAL MINIMU ENERGY MAXIMU M M KINETIC MAXIMU ZER ENERGY M O 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? Radio _______ Television _______ Car engine _______ Computer _______ Turbine _______ Motor _______ Transformer _______ Any electrical device _______

What happens to wasted energy? What happens to the wasted energy you get whenever energy is changed from one form to another? reated estroyed Remember energy can not be c______ or d_______. Wasted e_____ spreads out (d_______) into the nergy issipated s_____. urroundings This makes the energy harder to r____. e-use This is why it is important to r_____ the amount of educe wasted energy there is.

Energy Transfer diagrams 3/15/2018 Consider a light bulb. Let’s say that the bulb runs on 100 watts (100 joules per second) and transfers 20 joules per second into light and the rest into heat. Draw this as a diagram: “Input” energy 100 J/s electrical energy “Output” energy 20 J/s light energy 80 J/s heat energy (given to the surroundings)

Example questions Consider a kettle: 2000 J/s electrical energy Sound energy Wasted heat Heat to water 1) Work out each energy value. 3/15/2018 Consider a computer: 150 J/s electrical energy 10 J/s wasted sound 20 J/s wasted heat Useful light and sound 1) How much energy is converted into useful energy?

3/15/2018 Here is a more complex energy transformation diagram, the sort used by engineers. This one is for an aeroplane engine.

Choose appropriate words to fill in the gaps below: Energy is required to do ____. work joules Energy is measured in ____ (J) Energy cannot be created or ______ but can only destroyed change ____. form Kinetic energy is the energy possessed by _____ bodies. moving When an object is lifted up it gains gravitational potential _______ energy. Heat or _____ energy is often produced as a _____ thermal wasted energy form, dissipated to the surroundings. WORD SELECTION: potential moving joules thermal work wasted form destroyed

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 J Energy stored in 1 litre of petrol: 34, 000 J Energy used by the human body for 1 day: 10, 000 J Energy in 1 unit on electricity bill (costs 15 p): 3, 600, 000 J Energy in a typical chocolate bar: 1, 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 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 12 th January 2012 • Kinetic Energy – Ek • If you need to find me, I will usually be in my classroom SS 15 or the science office SS 3 • Next lesson I want to spend half the lesson building roller-coaster, you need your log on details.

Potential Energy – Copy this Gravitational potential energy is the energy an object has because of its position in a gravitational field GPE = mass x height x Change in height Ep Ep= gravitational potential energy J m = mass kg g = gravitational field strength N/kg h = height m m g h Now make mass, gravitational field strength and height the subject of the formulae

Rearranging the formulae Ep m g h

Ep= gravitational potential energy (J) m = mass (kg) g = gravitational field strength (Nkg-1) h = height (m) Ep m g h

Example Woof! (help!) 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?

On earth g = 10 m/s 2 Mass of dog = 12 kg Height = 3. 4 km = 3400 m Example

On earth g = 10 m/s 2 Example Mass of dog = 12 kg GPE of dog = mgh = 12 x 10 x 3400 = 408 000 J Height = 3. 4 km = 3400 m

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

Kinetic energy

Some example questions… 3/15/2018 How much gravitational potential energy have the following objects gained? : 1. A brick that weighs 10 N lifted to the top of a house (10 m), 2. A 10, 000 N car lifted by a ramp up to a height of 50 cm, 3. A 70 kg person lifted up 50 m by a ski lift. How much GPE have the following objects lost? : 1. A 2 N football dropping out of the air after being kicked up 30 m, 2. A 0. 5 N egg falling 10 m out of a bird nest, 3. A 10, 000 N car falling off its 50 cm ramp. 4. Mr Richards when bungi-jumping off a 110 -metre high bridge in Zambia in August

Energy changes

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 mass of the object x The height of the object x The velocity of the object The shape of the object © Boardworks Ltd 2003

Kinetic Energy Copy this E Ek = kinetic energy J m = mass kg v = speed m/s ½ k m v 2

Kinetic Energy Now make mass and velocity the subject of the equation E ½ Ek = kinetic energy J m = mass kg v = speed m/s k m v 2

Mass and speed If you increase the mass of a moving object you increase the kinetic energy. If you double the mass, you double the kinetic energy. If you increase the speed of a moving object you increase the kinetic energy. BUT… If you double the speed, you quadruple the kinetic energy. This is why even if you are slightly above the speed limit, you increase the kinetic energy of a moving car a lot, this means it is harder to stop the car and there is more chance of an accident. © Boardworks Ltd 2003

Kinetic energy calculation A car has a mass of 400 kg and a velocity of 10 ms-1, what is the kinetic energy of the car? Kinetic energy = ½ mass(velocity)2 = ½ x 400 x(10)2 = 20 000 J © Boardworks Ltd 2003

Example A 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? Ek = mv 2/2 = (0. 15 x (400)2)/2 = 12 000 J

Using conservation of energy • Now with a falling object as it falls faster and faster the potential energy is gradually converted to kinetic energy. At the moment just before impact, potential energy is zero and all the potential energy has been converted to kinetic energy we can use this to solve problems and find the velocity

Now a bit of algebra

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

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? Kinetic energy

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

Example GPE of dog = mgh = 12 x 10 x 3400 = 408 000 J KE at bottom = 408 000 J = mv 2/2 Just before the dog hits the ground, what has this GPE turned into? Kinetic energy

Example 408 000 = mv 2/2 Just before the dog hits the ground, what has this GPE turned into? Kinetic energy

Example 408 000 = mv 2/2 2 x 408 000 = 12 x v 2 Just before the dog hits the ground, what has this GPE turned into? Kinetic energy

Example 408 000 = mv 2/2 2 x 408 000 = 12 x v 2 816000 = 12 v 2 Just before the dog hits the ground, what has this GPE turned into? Kinetic energy

Example 408 000 = mv 2/2 2 x 408 000 = 12 x v 2 816000 = 12 v 2 68000 = v 2 Just before the dog hits the ground, what has this GPE turned into? Kinetic energy

Example 408 000 = mv 2/2 2 x 408 000 = 12 x v 2 816000 = 12 v 2 68000 = v 2 261 = v v = 261 m/s Assuming no energy is lost as air resistance – in reality the dog would have reached TERMINAL VELOCITY

Let’s try some questions! Stick them in first!

Homework th April Due next Thursday 14 Finish ALL questions on Kinetic and Gravitational energy

What type of energy is stored in a coiled spring? A. Sound B. Kinetic

What type of energy is stored in baked beans? A. Sound B. Gravitational C.

What is the change in gravitational potential energy of a weight of 60 N that moves through a distance of 6 m? A. 10 J B. 360 J C. 66 J D. 54 J © Boardworks Ltd 2003

What is the kinetic energy of a ball of mass 6 kg and velocity 5 ms-1? A. 75 J B. 30 J C. 1. 2 J D. 150 J © Boardworks Ltd 2003

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

Don’t forget! Test! • Use the revision sheet to help you study! • Test on Wednesday 2 nd February

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 experiment You will have 2 minutes on each example.

Ready?

Go!

Sankey Diagram A Sankey diagram helps to show 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 is defined as Efficiency (%) = useful energy output x 100 total energy input

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 Efficiency = 75 x 100 = 75% 100

Energy efficient light bulb Efficiency = 75 x 100 = 75% 100 That’s much better!

More complex examples

Let’s try some questions! Stick the sheet into your books and answer the questions