Unit 6 TYPES OF MECHANICAL NERGY

TYPES OF MECHANICAL ENERGY

There are two types of mechanical energy – potential energy and kinetic energy. Suppose a metal cylinder is lifted up and then released. It will fall. As it falls it can do a useful job. For example, it can drive a cuckoo clock before it is released.

The cylinder has energy. It is called potential energy. Sometimes it is called gravitational potential energy, because the object is lifted through the Earth's gravitational field.

If water is pumped from a large reservoir up to a small reservoir in the hills, it gains potential energy. As the water runs down again to the lower reservoir, it drives a turbine. This turbine turns a generator and so produces electricity.

Some clocks, watches and toys operate from energy stored in a coiled spring. When energy is stored by a change in position, it is called potential energy. The energy stored by the pumped water or the wound spring is potential energy.

When a car is moving it has motion energy or kinetic energy. Petrol is burned in the engine and gives the car this kinetic energy. It is difficult to make this energy do any other useful job. When the driver applies the brakes the car's kinetic energy is reduced. The brakes then become warm and the air around them is heated. The energy is wasted or "lost".

If a solid, liquid or gas is moving the substance has kinetic energy.