Chapter 37 - Work, Power and Energy Flashcards
What i the unit for work?
The Joule (J)1 joule = 1 Newton x 1 metre
What is the formula for work?
Work = force x distance
Energy
The ability to do work
What is the unit for energy?
Joule (J)
Kinetic energy
Moving objects have kinetic energy. A car travelling down the road has kinetic energy. The car is moving the passengers inside the car
Potential energy
Very often when you change the shape or position of an object you give the object potential energy. For example when you wind up the clock you tighten or change the shape of the spring. As the spring slowly rewinds to its original shape it moves the hands of the clock
Sound energy
When you hear somebody talking at the far side of the room sound energy travels from their vocal chords to your ears. For example when you listen to recorded music the diaphragm of the speaker vibrates. The vibration of the diaphragm generates sound
Heat energy
Heat energy can cause movement. For sample heat can cause the mercury inside a laboratory thermometer to move
Chemical energy
Chemical energy causing movement may not seem obvious at first. For example the food we eat contains the chemical energy we need to move or grow
Electrical energy
Electrical energy is a good example of a form of energy causing movement. For example the new generation of electric cars have very powerful motors to move the cars at speed
Magnetic energy
Most electric motors are examples of magnets causing movement Large powerful magnets are used in scrapyards to lift pieces of metal such as cars
Solar energy
Energy from the sun. For example photosynthesis is an excellent example of solar energy causing movement. The plants grow in size i.e. they move upwards
Nuclear energy
Generating electricity from nuclear energy is growing in popularity. In nuclear fission a nucleus of an atom is split and large amounts of energy are released. This energy can be converted into electrical energy
What is the principle of conservation of energy?
Energy is neither created nor destroyed but can be converted from one form to another
Power
The rate at which work is done
How do you calculate power?
work done Power = ———— time taken
What is the unit of power
Watt
Name 9 different forms of energy
Kinetic Potential Sound Heat Chemical Electrical Magnetic Solar Nuclear
Non-renewable sources of energy; explain and give examples
Sources that will eventually run out
- Oil
- Coal
- Gas
- Turf
What are the advantages of non-renewable sources of energy?
- Easy to get
- Reasonably cheap
What are the disadvantages of non-renewable sources of energy?
- Greenhouse gas emitions
- Polluting the atmosphere
Renewable sources of energy; explain and give examples
Sources that won’t run out
- Solar energy
- Hydro electricity
- Wind energy
- Nuclear energy
What are the advantages of solar energy?
- Doesn’t cause pollution
- Free
What are the disadvantages of solar energy?
- Not very efficient
- Solar cells are expensive to make
What is hydro-electricity?
It sits as potential energy as it is stored behind a dam. It then changes to kinetic energy as it flows out and is then converted into electricity
What are the advantages of hydro-electricity?
- No pollution
- Efficient
What are the disadvantages of hydro-electricity?
-Flooding
What are the advantages of wind energy?
- No pollution
- Free
What are the disadvantages of wind energy?
- No electricity produced on a calm day
- Propellers are noisy and spoil the natural beauty of the countryside
What are the advantages of nuclear energy?
- Using a fuel in plentiful supply
- Reduces present level of greenhouse gas emitions
What are the disadvantages of nuclear energy?
- Nuclear explosion
- Radioactive waste
How is the sun our primary source of energy?
○Fossil fuels come from dead plants and animals that needed the sun to survive
○The food we eat for energy needs the sun for photosynthesis
○Weather conditions are linked to the sun
○Geothermal energy -> no sun, no heat
