A bucketful of water is to be drawn from a well. Work will be done when a force is applied to do this, because there will be a displacement of water.

If a ball is dropped on the sloping roof of a house, it acquires motion and falls on the ground. That is, transformation of potential energy into kinetic energy takes place.

You might have seen some beautiful fireworks during Diwali. It is an example of transformation of chemical energy into light energy.

The solar cooker is an application of the heat energy of the sun, while solar cells, solar lamps are applications of the light energy of the sun.

One labourer carried four pans of road metal through a distance of 100 metres. If he carries two pans of road metal through a 200 metre distance equal work will be done.

The capacity that an object has for doing work is called energy.

When the position of any object changes, then we can say that displacement has taken place.

While measuring work, the magnitude of force applied on an object and the displacement of an object should be taken into account.

Mechanical energy: Kinetic and potential energy are two types of mechanical energy, Light energy, Heat energy, Muscular energy, Sound energy, Magnetic energy, Electrical energy, Chemical energy, Nuclear energy are the various forms of energy

Plants prepare food by utilizing solar energy. The food produced is in the form of chemical energy. This food is consumed by animals. They develop muscular energy. The digestion of food also produce heat energy in the body.

This natural chain of transformation of energy can be shown as follows :

We should save energy because of the following:

• Saving energy is the need of the hour.
• Wasting energy is same as wasting money. We all know that electricity we use at our homes isn't free but costs us a lot. So, saving energy will save money too. 
• When we produce energy, we need fuel on a very large scale. The fuels are also depleting fast from the earth.
• By more consumption of energy, lots of carbon dioxide is produced. This leads to global warming and pollution.
• In order to conserve our environment, we must save energy.

The forms of energy which do not produce smoke and carbon gases such as carbon dioxide or carbon monoxide are known as green energy.

Non-conventional energy resources are inexhaustible in nature and can be used in various forms again and again. For example, Solar energy, wind energy, tidal energy, hydel power, atomic energy, energy obtained from the oceanic waves.

Heat and light energy of Sun are used in solar energy devices.

• In solar cooker, solar heater and solar dryer, the heat energy from the sun is used.
• In solar lamps light energy from solar energy is used. In solar cells, solar energy is used to produce electricity.

• The non-conventional energy resources are renewable energy resources.
• They are inexhaustible and continuously available resources.
• On the other hand the traditional non-renewable energy resources such as fossil fuels are getting fast depleted.
• Fossil fuels also create pollution and problems like global warming and climate change when used in excess.
• In order to save our earth and environment, we must maximize the use of non-conventional energy resources.

Wind is the odd one out because it is a renewable energy resource. The rest are non-renewable energy resources.

A book kept on a table is the odd one out because no work is being done in this case. In rest of the cases showing displacement and thus possess kinetic energy.

Petrol is the odd one out as it is a conventional energy resource. The rest are non-conventional energy resource.

Putting off the light when going out is the odd one out because it is one of the measures of saving energy. The rest involves actions of wasting energy.

Potential, kinetic, heat, sound, wind, water, light.