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Natural sciences

Grade 9

Energy: forces and machines

Module 21

Work and conversion of energy

Activity 1:

Describing the relationship between effort and energy with reference to a turbine

[LO 1.2, 2.1, 3.2]

Energy is necessary for any performance of work. This energy must be obtained from FUELS or from CONVERTED forms.


  • Use a tin lid, cut it into segments to form it into a fan and make a hole in the centre.
  • Nail the fan to a piece of wood.
  • Boil water in a kettle, until there is a strong draught of steam.
  • Hold the fan in position so that the jet of steam will be directed towards its centre.

1. What happened?

2. What kind of energy conversion occurred?

3. Describe the form of energy conversion that occurs with wind towers such as those that have recently been erected along the West Coast in the vicinity of Malmesbury.

4. What advantages do wind towers like these have for the environment?

  • Write a paragraph (60 words) about the value that the principle of the turbine has for people.
  • WORK is also measured in (give the name of the unit) .…………....................................

Activity 2

Discussing other machines that operate by means of conversion of energy


  • As long ago as the early 17 th century, Robert Hook assumed that light rays have energy and that a wound-up spring has potential energy. He also constructed the first microscope and was the first person to use the universal lever, which is used in a wide range of instruments and cars.


  • Satellites depend on solar panels to absorb light energy from the sun and supply electricity for all other electronic functions and for cameras and radio equipment. Energy is also stored in chemical form in rechargeable batteries.


  • The blades of the rotary disk are turned by the wind to drive a pump that pumps underground water to a storage dam.


  • Name at least three other machines that operate by means of energy conversion and explain the workings of each one.


  • When a machine or appliance fails to provide an adequate quantity of the energy that it has been designed to provide we say that it is in affective.
  • The light bulb, for instance, releases (unwanted) heat, but was actually designed to provide light!
  • In this instance, fluorescent lighting is more effective and economical.
  • Are you able to list further examples?


LO 2
Scientific KnowledgeThe learner will know and be able to interpret and apply scientific, technological and environmental knowledge.
This is displayed when the learner:
2.1 is able to recall meaningful information;
2.2 is able to arrange information according to categories;
2.3 is able to interpret information;
2.4 is able to apply knowledge.
LO 3
Science, Environment and the CommunityThe learner will be able to demonstrate an understanding of the interrelationships between science and technology, society and the environment.
This is displayed when the learner:
3.1 is able to show appreciation of science as a human endeavour;
3.2 is able to recognise the value of sustainable utilisation of resources.


Activity 1


1. The fan (‘turbine’) rotates

2. Chemical to steam to kinetic / mechanical

3. Kinetic to electrical to chemical

4. Natural resources (e.g. coal) are not used and pollution is avoided


  • E.g. natural energy is converted to usable energy
  • Without consumption of resources
  • Without pollution
  • There are no waste products to be got rid of
  • Examples of utilising turbines: generation of electricity, previously also for driving mills

Effort is measured in Joule

Activity 2

  • Any power generator
  • Compressor
  • Vehicle engine
  • Sewing machine
  • Kitchen appliances
  • Etc.
  • Ineffective machines: any machine or system that releases energy in a non-usable form, e.g. a car that is driven with the hand break on (much energy is wasted in the attempt to overcome the force of friction – energy in the form of heat goes to waste).

Questions & Answers

pls who is a consumer
Cobby Reply
whoever use the product can be the consumer either the buyer of it or people at home who will be using the product
compensation of goods and services by a customer with price that willing to satisfy themselves.
who describe economic
yao Reply
Stanley Reply
pls I'm a home economic student and went I was in my formal school I was doing biology so wen I got she 2 and I went a different school and that school they don't do biology what they do is economics and I don't understand it cos I didn't learn from form one so I will need ur help in this please
Hawa Reply
what help u need
I don't understand it I tried to learn from form one but still don't understand
jxt follow the notes well try solving question under it
important of economics
Benita Reply
what is supply chain
Jos Reply
what is financial management? And why is it necessary in business ?
Fatema Reply
it is the managing of all transactions that take place in any business and if not managed properly it could create debts and destroy the business
What is demand?
Annonymous Reply
why is degree important in economics
Ebunoluwa Reply
important of enocomic
Adu Reply
what is division of labour
Dennis Reply
division of labour can be defined as the separation of task to individuals in any economic system to specialize on it.
what is demand curve
Victoria Reply
demand curve is a downward sloping economic graph that shows the relationship between the price of product and the quantity of the product demanded.
What is demand
Frank Reply
It refers to the quantity of a commodity purchased in the market at a price and at a point of time.
refers to amount of commodities a consumer is willing and able to buy at particular price within a period of time
It is the ability and willingness a customer buys a product or service at a particular price, place and time while other things remaining constant or the same
It refers to the quality of a commodity purchased in the market at a price and at a point of time .
demand refers to the quantity of goods and services a consumer is willing and able to buy at a given price within a a specific period of time
In which case is opportunity cost is zero
Francis Reply
where no alternative is available
who is the father of economic
Omar Reply
Adam Smith
Adam Smith
Adam smith
Adam Smith
Researchers demonstrated that the hippocampus functions in memory processing by creating lesions in the hippocampi of rats, which resulted in ________.
Mapo Reply
The formulation of new memories is sometimes called ________, and the process of bringing up old memories is called ________.
Mapo Reply
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Source:  OpenStax, Natural sciences grade 9. OpenStax CNX. Sep 15, 2009 Download for free at http://cnx.org/content/col11069/1.1
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