A machine's efficiency is a measure of how efficiently it eliminates friction. It is determined as the percentage of input work that is converted into output work. The mechanical advantage of a machine is the number of times the input force is multiplied. For example, if a screw has a mechanical advantage of 3, then for every three turns of the handle you will get as much movement in the screw as there were turns on the handle. Therefore, the efficiency of a screw motor is 33%. Of the energy supplied to the motor, one third goes into driving the screw and two thirds is lost as heat. The efficiency of a machine depends on many factors such as speed, size, load, type of drive mechanism, etc. Generally, the higher the speed, the lower the efficiency will be. Large machines are more efficient than small ones - this is because less effort is needed to produce a given amount of power at high speeds. If a machine is operating at a low speed, but producing a large amount of force, its efficiency is high even though it is losing some energy due to frictional forces. Efficiency can also be defined as the output work divided by the input work. This definition does not take into account any potential losses within the system. For example, if a machine is working with 100% efficiency but loses 10% of its energy due to frictional forces, its actual efficiency would be 90%.