Simple machines enable people to do work more quickly and easily. However, that does not mean that all machines use 100% of their potential energy to do the work; it just means that they do the work more effectively than it could be done without the machine at all. In this activity, you will learn more about the benefit of using machines that are energy efficient.

The law of conservation of energy states that energy can be neither created nor destroyed. So, if a machine is not 100% efficient, where does the leftover energy go?

Machines lose energy in three common ways: through friction, heat, and incomplete combustion.

Friction

When parts of a machine touch, they lose energy through friction. Friction is the way the two parts resist movement against each other. Friction is a force that acts in an opposite direction to the movement (force). This is the way most simple machines lose efficiency. For example, when we push a load of boxes up an inclined plane to load it into a truck, friction occurs between the ramp and the dolly even though the wheels are turning.

 

  

Heat

When a machine needs to be cooled to keep it working properly, some of its energy is lost to its cooling system. Other machines lose heat through their exhaust systems. Loss of efficiency through heat loss is common in many compound machines such as motors and gearboxes of cars, trucks, and equipment.

Incomplete Combustion

When an engine is not working efficiently, it does not burn all the fuel it uses. It emits smoke or exhaust instead. Again, this type of energy loss is seen with compound machines rather than simple machines. Note the black cloud of carbon from some diesel engines!