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TECHNOLOGY
Guess this! What is the word for the ability to do work? What can neither be created of destroyed? What can only be transferred from one form to another? You are correct:
E_______________________
The main source of energy in nature is the sun , because it radiates heat and light energy. Plants use this light and heat energy and change it into chemical energy, which they use for growing.
People and animals also use energy for everything that they do. We obtain energy by eating food. The chemical energy that is trapped in food is converted into kinetic energy (motion) inside our bodies. This makes it possible for the muscles of our bodies to do their work.
All the foods that we eat therefore contain energy, to a lesser or greater degree. Can you name the unit that is used to measure the amount of energy that is contained in food?
Study the labels on tins and boxes containing food. Complete the following table to determine the energy value of different kinds of food:
| FOOD | QUANTITY, e.g. 100g | KILOJOULES per 100g |
Which food types contain the highest amount of kilojoules per 10 g/ml?
Foods like fats, oils, proteins, sugar and starches are able to supply the body with energy. Sugar and starch (carbohydrates) supply more energy and do this faster than other foods. If you do not get enough exercise and therefore do not manage to get rid of this energy, excess energy is stored in your body as fat .
Why would an athlete who takes part in a race like the Comrades Marathon, eat pasta before the race?
Food supplies energy for us to be able to do work. Machines also need energy to be able to work.
There are many different kinds of energy, namely:
| Chemical energy | An object has the ability to exhibit energy because of its chemical composition. |
| Potential energy | Any object that is not on the earth’s surface has the ability to return (fall back) to the earth because of the earth’s force of attraction. |
| Kinetic energy (motion) | The energy of a moving object. |
| Heat energy | An object’s ability to radiate warmth. |
| Light energy | An object’s ability to radiate light. |
| Electrical energy | An object’s ability to conduct electricity. |
| Sound energy | An object’s ability to produce sound. |
Transfer of energy occurs continuously in objects. We speak of this as the conversion of energy.
Assignment 4
Energy conversion takes place in the following appliances and objects: a stove, a high fidelity system, a light bulb, a ball attached to a length of elastic, an electric train, a car battery. Match these examples to the different kinds of energy conversion listed below.
We are going to use this module to examine electric energy. Electricity is very useful, because it is a type of energy that can easily be converted to other forms of energy. It does not pollute or damage the environment and can be stored easily and safely.
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