Energy

It is often helpful to think of the designer as working in three different kinds of medium – materials, energy and information. Materials are the most readily appreciated, but it is convenient to study energy first because it introduces ideas which are essential to the consideration of materials: information is left until Chapter 6.

An aircraft can fly the Atlantic because it can store a great deal of energy in chemical form in fuel and convert that energy reasonably efficiently into other forms as required. An aircraft or a bird can take off and fly because of its ability to convert or release energy at a high rate – the rate of conversion or release of energy is called power.

The ability of a bird or a mammal to survive in cold weather depends on its ability to keep down its loss of heat, which is a form of energy, and the protection that a vehicle offers its occupants in a collision depends largely on the capacity of its structure to absorb the destructive energy of motion (kinetic energy). All life depends on energy: plant life draws its energy from the rays of the sun, and animals in turn obtain energy by eating plants or other animals. At another extreme, a clothes-peg or a nut-and-bolt depend for their functioning on their power of storing a little energy, as we shall see.