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Year 8 Science Revision (Unit 5)
year 8 science revision
Energy types and sources
Energy transformations
Gravitational potential energy
Energy types and examples
ANSWERS:
An energy transformation is when energy changes form from one type to another
Write down a list of the 9 types of energy and an example of where you would find each
1. Heat (sun)
2. Light (light bulb)
3. Sound (guitar)
4. Nuclear (atoms)
5. Kinetic (dancers dancing)
6. Chemical (food)
7. Potential (fuel in a fuel tank)
8. Electrical (lightning)
9. Tidal and wind energy (waves)
Complete the table below in your book
Imagine you wanted to go on the biggest waterslide at Wet n' Wild
- You would use Kinetic energy to walk up the steps to the top of the slide
- At the top of the slide before you slid down you would have gravitational potential energy
- As you slid down you would have kinetic energy
CALCULATING GRAVITATIONAL POTENTIAL ENERGY
ALTERNATIVE ENERGY SOURCES
HEATING PLAIN/SALTY WATER EXPERIMENT
We need to develop alternatives to fossil fuels because:
= mass x gravity x height
Remember: CMS = IDC
Gravitational potential energy
CALCULATING KINETIC ENERGY
Units of measurement for energy
- Burning these fossil fuels is harmful to the environment
- Our supply of fossil fuels is running out
- amount of salt in water
2
GPE = m x g x h
(assume gravity = 10m/s )
Change (independent) measure (dependent) same (controlled)
- temperature of water
CALCULATING ENERGY IN FOOD
Alternative energy sources (wind power, solar power)
- same amount of water, same beaker used, heated in same way
Kinetic energy = 1/2 x mass x velocity squared
Energy content (kj)
Food (100g)
Example question: A girl who weighs 50kg and has a gravitational potential energy of 500J is sitting at the top of a tree - calculate the height of the tree
_______________________
- Are renewable (never run out) and are less harmful to the environment BUT
- Can be very expensive to build and are often not very efficient (don't produce much energy)
- Energy is measured in Joules
- The symbol for Joules is (J)
- 1000 Joules = 1 kilojoule
This was a fair experiment because we only had one independent variable, everything else was a controlled variable
2
KE = 1/2 x m x v
100
Apple
Yoghurt
500
ENERGY CHAINS
1000
Cupcake
An ordered list of energy types showing how energy has been transformed
Example question: Find the kinetic energy of a boy with a mass of 50kg running at 3m/s (Show all of your working out)
The yoghurt has less energy than the cupcake but more energy than the apple
For example: Turning on a light switch
energy
Chemical > kinetic > electrical > light
energy
energy
For example: Playing with a wind up toy
Which has the most energy: 50g of cupcake, 75g of apple or 60g of yoghurt?
energy
chemical > kinetic > elastic potential > kinetic
energy
energy