Tag: form 4 Integrated Science revision

In order for mankind to be productive people should be healthy. Complete health combines the physical, mental and social well-being of an individual. Maintaining good health involves eating a balanced diet. A balanced diet provides all the nutrients required by the body in the right proportions. Different nutrients may be required in different proportions according to the age, sex and activity of the individual. Sick people may also need special diets. There are a number of diseases that are caused by malnutrition due to wrong, excessive eating and undernourishment.

A device that makes work easier by reducing effort required increasing distance, or changing the direction of  the force.

The human race is always trying to find ways of making work easier. Machines are devices that make work easier. The principle involves lessening the effort required to lift or move a load or changing the direction in which the force is applied to a more convenient one. Levers and pulley systems help to move loads using by reducing the effort required. Mechanical advantage is the ratio of the load to the effort. A large mechanical advantage indicates that a much smaller effort is required to lift a heavier load.  Friction affects the way machines work and their efficiency. Pumps use the concept of pressure  to move fluid substance and act as machines.

Human life is enhanced by structures. Every structure has a design that makes it best suited for its purpose and the material chosen to make the structure must have suitable properties.  Beams are used to carry loads.  A truss is made up of several beams joined together.  Different building materials have their advantages and disadvantages. There are a variety of methods of joining materials.

Human life is enhanced by structures. Every structure has a design that makes it best suited for its purpose and the material chosen to make the structure must have suitable properties.  Beams are used to carry loads.  A truss is made up of several beams joined together.  Different building materials have their advantages and disadvantages. There are a variety of methods of joining materials.

Solar energy refers to energy from sun. Solar energy has three main components; visible light, infrared radiation and ultraviolet radiation. Visible light enables us to see, ultraviolet radiation enables the skin to produce vitamin D while infrared (radiant heat) warms up objects and heats up any object which absorbs it. Solar energy absorbed by plants enables them to manufacture food through the process of photosynthesis. When solar energy strikes an object, it is either reflected if surface is polished, e.g. a mirror or it is absorbed.

There are negative and positive charges. Like charges repel while opposite charges attract. Materials can be rubbed or brushed to transfer charge to them.  Lightning is the result of movement of electrical charge from the clouds to the ground. Current electricity is the result of flowing charge. Cells convert chemical energy into electrical energy. Electrical energy is hazardous and safety precautions should be observed when it is used.

Fuels are materials that are burnt to provide heat or chemical energy. Fuels can be gases, liquids or  solids. There are natural and man-made fuels. Some fuels are more efficient than others. Engines are machines designed to convert chemical energy into other forms of energy and thus do work. The use of fuels has social and economic implications on society. Fuels are either renewable or non-renewable. Non-renewable fuels should be used sustainably.