Conservation of Energy 03/08/2019 Conservation of Energy 2016 EdExcel GCSE Physics Topic 3 W Richards The Weald School

Gravitational potential The 9 types of energy 03/08/2019 Type 3 example sources Type 3 example sources Heat Kinetic (movement) Nuclear Sound Light Chemical Electrical Gravitational potential Elastic potential

Gravitational Potential Energy 03/08/2019 To work out how much gravitational potential energy (GPE) an object gains when it is lifted up we would use the simple equation… GPE = mass x grav. field strength x Change in height (Joules) (newtons) (N/Kg) (metres) GPE H mg You need to learn this equation!!

Some example questions… 03/08/2019 How much gravitational potential energy have the following objects gained?: A brick of mass 1kg lifted to the top of a house (10m), A 1,000kg car lifted by a ramp up to a height of 2m, A 70kg person lifted up 50cm by a friend. How much GPE have the following objects lost?: A 0.2kg football dropping out of the air after being kicked up 30m, A 0.05kg egg falling 10m out of a bird nest, A 1,000kg car falling off its 200cm ramp. 100J 20KJ 350J 60J 5J 20KJ

Kinetic energy KE = ½ mv2 Kinetic energy = ½ x mass x speed squared 03/08/2019 Any object that moves will have kinetic energy. The amount of kinetic energy an object has can be found using the formula: Kinetic energy = ½ x mass x speed squared in J in kg in m/s KE = ½ mv2 You need to learn this equation!!

Example questions 03/08/2019 Lydia drives her car at a speed of 30m/s. If the combined mass of her and the car is 1000kg what is her kinetic energy? Sam rides her bike at a speed of 10m/s. If the combined mass of Sam and her bike is 80kg what is her kinetic energy? Josh is trying to catch a bus and is running at 3m/s. If he has a mass of 60kg how much kinetic energy does he have? A 2000kg car is being driven at a speed of 10m/s. If it doubles its speed to 20m/s what happens to the car’s kinetic energy? 450,000J 4000J 270m/s Increases from 100,000J to 400,000J

Example questions (higher) 03/08/2019 Steve is running away from the police and has 100J of kinetic energy. If he is running at 2m/s what is his mass? James is driving in his car and has a combined mass of 1200kg. If he has 540KJ of kinetic energy what speed is he driving at? Dave is running and has a kinetic energy of 750J. If his mass is 60kg how fast is he running? Stuart is spotted walking around Tescos. If he has a kinetic energy of 150J and he’s walking at a pace of 2m/s what is his mass? 50kg 30m/s 5m/s 75kg

The Laws of Physics 03/08/2019 There are many laws of physics, but one of the most important ones is: Energy cannot be created or destroyed, it can only be converted from one form to another

Electricity Light + heat Energy changes 03/08/2019 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 What are the energy changes for the following…? An electric fire A rock about to drop An arrow about to be fired

An example energy change - A skydiver 03/08/2019 An example energy change - A skydiver Here’s a skydiver: If the skydiver has reached terminal speed explain what happens to his… Kinetic energy Gravitational potential energy …while he is falling.

Example energy change 2 - Elastic Potential Energy 03/08/2019 03/08/2019 Example energy change 2 - Elastic Potential Energy Elastic potential energy is the energy stored in a system when work is done to change its shape, e.g: Describe the energy changes when the mass is: At the top of it’s movement In the middle At the bottom

Energy Transfer Examples Look at the following objects and write down what their energy changes are: a) Electric Light Bulb b) Battery c) Hairdryer d) Candle Burning e) Model Car (Wind-up) f) Dynamo g) Yo-Yo h) Radio i) Kettle j) Dropping a Golf Ball

Energy Transfer Diagrams 03/08/2019 Here’s a way to illustrate the energy changes of a device (let’s say a TV for example): Light (80J) Electrical Energy (200J) Sound (40J) Heat (?) Draw energy transfer diagrams for: A light bulb A hairdryer A burning candle

Conservation of Energy 03/08/2019 In any energy change there is ALWAYS some “waste” energy: e.g. a light bulb: Electricity Light + heat In this example HEAT is wasted and it is transferred to the surroundings, becoming very difficult to use. Describe the following energy changes and state the “waste” energy or energies: A vacuum cleaner A TV A dynamo/generator

Which bulb is wasted the most heat energy? 03/08/2019 Which bulb is wasted the most heat energy?

Examples of wasted energy 03/08/2019 Clearly, not all of the energy from the fuel put into this car will become movement energy. Where is energy wasted in this car? The bulb on the left is an “energy efficient” one. Why is the bulb on the right wasting energy?

Ways to reduce heat loss 03/08/2019 Q. How would you reduce energy loss in these objects?

Heat loss through walls 03/08/2019 I’m worried about how much heat I’m losing through my walls. What can I do to reduce this? Here’s a new building with cavity wall insulation being installed: How does the use of cavity wall insulation help keep a building warmer? The rate of heat loss through a wall depends on two things: How thick the wall is The thermal conductivity of the wall

You need to learn this equation!! Efficiency 03/08/2019 Efficiency is a measure of how much USEFUL energy you get out of an object from the energy you put INTO it. For example, consider a TV: Light (80J) Electrical Energy (200J) Sound (40J) Heat (?) Efficiency = Useful energy out Energy in x100% You need to learn this equation!!

Some examples of efficiency… 03/08/2019 5000J of electrical energy are put into a motor. The motor converts this into 100J of movement energy. How efficient is it? A laptop can convert 400J of electrical energy into 240J of light and sound. What is its efficiency? Where does the rest of the energy go? A steam engine is 50% efficient. If it delivers 20,000J of movement energy how much chemical energy was put into it? 2% 60%, given out to the surroundings as heat 40,000J

Increasing Efficiency (HT only) Earlier on in this unit we considered these energy changes. How could we increase the efficiency of these devices? a) Electric Light Bulb b) Battery c) Hairdryer d) Candle Burning e) Model Car (Wind-up) f) Dynamo g) Yo-Yo h) Radio i) Kettle j) Dropping a Golf Ball

Fuels 03/08/2019 A “fuel” is something that can be burned to release heat and light energy. The main examples are: Coal, oil and gas are called “fossil fuels”. In other words, they were made from fossils.

Renewable and non-renewable sources 03/08/2019 A ___________ energy source is one that when it has been used it is gone forever. The main examples are ____, oil and gas (which are called ______ ____, as they are made from fossils), and nuclear fuel, which is non-renewable but NOT a fossil fuel. A renewable energy source is clearly one that can be _______ (“renew = make again” or “replenish”), e.g. _____, solar power etc. Words – non-renewable, coal, fossil fuels, wood, renewed Q. What do we use energy sources for? Why do we need them?

The problem with fossil fuels… 03/08/2019

Pollution 03/08/2019 When a fuel is burned the two main waste products are _____ dioxide and ________ dioxide. Carbon dioxide is a _________ ___ and helps cause _______ _________. This is produced when any fossil fuels are burned. Sulphur dioxide, when dissolved in ________, causes ______ _____. This is mainly a problem for ___ power stations. Nuclear power stations do not produce these pollutants because they don’t ____ fossil fuels. Words – sulphur, coal, global warming, carbon, acid rain, greenhouse gas, rainwater, burn

Non-renewable energy sources 03/08/2019 Advantages Disadvantages Cheap fuel costs Pollution – CO2 leads to global warming and SO2 leads to acid rain Good for “basic demand” Coal, oil, gas and nuclear Reliable Nuclear produces little pollution Fuel will run out

Renewable Sources of Energy- Biomass 03/08/2019 Renewable Sources of Energy- Biomass

03/08/2019 Wind Power

Tidal Power 03/08/2019 High tide Low tide

Wave Power 03/08/2019

Hydroelectric Power 03/08/2019

Solar Panels and Thermal Towers 03/08/2019 Solar Panels and Thermal Towers

Geothermal Energy 03/08/2019

Renewable energy sources summary 03/08/2019 Advantages Disadvantages Zero fuel costs Unreliable (except for hydroelectric) Don’t produce pollution Wind, tidal, hydroelectric and solar Expensive to build Can be replenished/ won’t run out May involve damaging the local environment Solar is good for remote locations (e.g. satellites)

Energy Supply in the UK 03/08/2019 What conclusions can you draw from the following information? What good or bad points can you draw from this information?