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Natural sciences

Grade 4

Energy and change

Module 28

Making energy available to people


Energy from sunlight is stored in and around the earth in several ways. (In some instances temporarily, as when the earth is warmed by the sun, or for longer periods of time, for instance when it is fixed in food). The stored energy can be released later and be used.

Let us take a look at some of the means by which it may be released


Using wind as a source of energy to our advantage

[lo 1.1, 1.2, 1.3, 2.1]

See how many of the following idiomatic expressions that have developed around the idea of wind are known to you?

  • We got wind that you were coming (we were given a hint)
  • His talk was all wind (it was insubstantial)
  • Between wind and water (a vulnerable spot, as the part of a ship that is normally below water but is exposed when the ship rolls)
  • How the wind blows (what appears probable)
  • In the wind (about to happen)
  • Three sheets in the wind (intoxicated or drunk)
  • Sail close to the wind (come near the limits of danger)
  • Take the wind out of someone’s sails (destroy someone’s advantage)

What is wind?

Blow on your hand. What do you notice?

We cannot see the wind, but we can feel it when it blows against our faces or ruffles our hair.

Washing dries quickly if it is hung out in the wind.

Do you know the reason for this?

How does wind occur?

Complete the sentences to explain the illustration by supplying the missing words:

  1. By day the sun . It .

the land.

  1. Warm air .
  2. Cooler air moves from the to the

to take the place of the warm air.

  1. This is how originates.

Make a windmill

  • Use stiff paper. Cut it according to the instructions on the illustrations.
  • Will this windmill turn in a room where there is no wind?
  • What could you do to make it turn?
  • Discuss suggestions about how to increase the windmill’s turning speed with your friends and report your ideas to the class.

Folding a small paper glider:

  • Fold a sheet of A4 paper in half lengthways.
  • Unfold the sheet of paper and fold the two top corners to the central fold so that the top edges lie together.
  • Fold the new corners to the central fold, forming a sharp arrow point.
  • Fold back the arrow point to the point at which the other points meet.
  • Fold along the original lengthways fold again to “close” the structure.
  • Fold the bottom corners separately to form wings.
  • Fold back both wings along a line lying parallel to the central fold.
  • Hold below and throw gently, noting how far the glider glides!
  • You may experiment to see which folding pattern allows the glider to glide better. Demonstrate this to the class and motivate your explanation.

Ways in which wind is used to the benefit of people

People have always made use of the power of wind to achieve things.

People have used the wind to their advantage. Sailors use the power of the wind that blows against their sails to drive their ships.

Windmills have been used to grind wheat and wind pumps pump water from below the ground.

The wind blows against the sails of the mill or the vanes of the wind pump to turn them. This turning turns machinery inside the mill. Modern windmills are called turbines and are used to provide electricity.

Class project

Let’s build a kite! First name and describe the materials that we could use for this project. Then form groups to build kites.


LEARNING OUTCOME 1: SCIENTIFIC INVESTIGATIONSThe learner will be able to act confidently on curiosity about natural phenomena, and to investigate relationships and solve problems in scientific, technological and environmental contexts.

Assessment Standard

We know this when the learner

1.1 plans investigations;

  • leads investigations and collects data;
  • evaluates data and provides feedback on observations.


The learner will know and be able to interpret and apply scientific, technological and environmental knowledge.

Assessment Standard

We know this when the learner

2.1 recalls significant information.


What is wind?

I feel air on my hand.

The wind shakes drops of water from the washing. The vapour from the washing disappears into the air.

Where does the wind come from?

Complete the sentences by using the missing words in order to explain the illustration:

1. shines, warm

2. rises

3. sea, land

4. wind

Make a windmill

Use a sheet of firm paper. Fold it according to the instructions on the illustrations.

Does a windmill turn in a room where there is no air current (wind)? No!

What can you do to make it turn? I can run while holding it in the air.

Questions & Answers

What is price elasticity of demand and its degrees. also explain factors determing price elasticity of demand?
Yutansh Reply
Price elasticity of demand (PED) is use to measure the degree of responsiveness of Quantity demanded for a given change on price of the good itself, certis paribus. The formula for PED = percentage change in quantity demanded/ percentage change in price of good A
its is necessarily negative due to the inverse relationship between price and Quantity demanded. since PED carries a negative sign most of the time, we will usually the absolute value of PED by dropping the negative sign.
PED > 1 means that the demand of the good is price elasticity and for a given increase in price there will be a more then proportionate decrease in quantity demanded.
PED < 1 means that the demand of the good is price inelasticity and for a given increase in price there will be a less then proportionate decrease in quantity demanded.
The factors that affects PES are: Avaliablilty of close substitutes, proportion of income spent on the good, Degree of necessity, Addiction and Time.
Calculate price elasticity of demand and comment on the shape of the demand curve of a good ,when its price rises by 20 percentage, quantity demanded falls from 150 units to 120 units.
Helen Reply
5 %fall in price of good x leads to a 10 % rise in its quantity demanded. A 20 % rise in price of good y leads to do a 10 % fall in its quantity demanded. calculate price elasticity of demand of good x and good y. Out of the two goods which one is more elastic.
what is labor
Grace Reply
labor is any physical or mental effort that helps in the production of goods and services
what is profit maximizing level of out put for above hypothetical firm TC = Q3 - 21Q2 + 600 + 1800 P = 600 MC = 3Q2 - 42Q + 600
Sosna Reply
consider two goods X and Y. When the price of Y changes from 10 to 20. The quantity demanded of X changes from 40 to 35. Calculate cross elasticity of demand for X.
sorry it the mistake answer it is question
consider two goods X and Y. When the price of Y changes from 10 to 20. The quantity demanded of X changes from 40 to 35. Calculate cross elasticity of demand for X.
The formula for calculation income elasticity of demand is the percent change in quantity demanded divided by the percent change in income.
what is labor productivity
Lizzy Reply
if the demand function is q=25-4p+p² 1.find elasticity of demand at the point p=5?
Puja Reply
what are some of the difference between monopoly and perfect competition market
Obeng Reply
n a perfectly competitive market, price equals marginal cost and firms earn an economic profit of zero. In a monopoly, the price is set above marginal cost and the firm earns a positive economic profit. Perfect competition produces an equilibrium in which the price and quantity of a good is economic
what are some characteristics of monopoly market
Obeng Reply
explicit cost is seen as a total experiences in the business or the salary (wages) that a firm pay to employee.
Idagu Reply
what is price elasticity
it is the degree of responsiveness to a percentage change in the price of the commodity
economics is known to be the field
John Reply
what is monopoly
Peter Reply
what is taxation
is the compulsory transfer of wealth from the private sector to the public sector
why do monopoly make excess profit in both long run and short run
Adeola Reply
because monopoly have no competitor on the market and they are price makers,therefore,they can easily increase the princes and produce small quantity of goods but still consumers will still buy....
how to identify a perfect market graph
Adeola Reply
what is the investment
investment is a money u used to the business
investment is the purchase of good that are not consumed today but are used in the future to create wealth.
investment is the good that are not consumed
What is supply
 Supply represents how much the market can offer.
it is the quantity of commodity producers produces at the market
what is the effect of scarce resources on producers
Phindu Reply
explain how government taxes and government producer subsidies affect supply
what is economic
Charles Reply
what are the type of economic
macroeconomics,microeconomics,positive economics and negative economics
what are the factors of production
process of production
Basically factors of production are four (4) namely: 1. Entrepreneur 2. Capital 3. Labour and; 4. Land but there has been a new argument to include an addition one to the the numbers to 5 which is "Technology"
what is land as a factor of production
what is Economic
economics is how individuals bussiness and governments make the best decisions to get what they want and how these choices interact in the market
Economics as a social science, which studies human behaviour as a relationship between ends and scarce means, which have alternative uses.
Economics is a science which study human behaviour as a relationship between ends and scarce means
Economics is a social sciences which studies human behavior as a relationship between ends and scarce mean, which have alternative uses.....
While the American heart association suggests that meditation might be used in conjunction with more traditional treatments as a way to manage hypertension
Beverly Reply
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Source:  OpenStax, Natural sciences grade 4. OpenStax CNX. Sep 18, 2009 Download for free at http://cnx.org/content/col11096/1.1
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