Mechanical load

Load, in mechanics, is the external mechanical resistance against which a machine, such as a motor or engine, acts. The load can often be expressed as a curve of force versus speed. Load, in mechanics, is the external mechanical resistance against which a machine, such as a motor or engine, acts. The load can often be expressed as a curve of force versus speed. For instance, a given car traveling on a road of a given slope presents a load which the engine must act against. Because air resistance increases with speed, the motor must put out more torque at a higher speed in order to maintain the speed. By shifting to a higher gear, one may be able to meet the requirement with a higher torque and a lower engine speed, whereas shifting to a lower gear has the opposite effect. Accelerating increases the load, whereas decelerating decreases the load. Similarly, the load on a pump depends on the head against which the pump is pumping, and on the size of the pump. Similar considerations apply to a fan. See Affinity laws.