A door belongs to the second class of levers because its pivot (hinge) is at the end, the load (weight of the door) is at the center, while the effort (opening the door) is applied at the other end. A wheelbarrow is also a second-class lever.
In a first-class lever, the pivot is placed between the effort and the load. Examples include: a crowbar, balance scale and seesaw. The effort of third class levers is applied between the load and the pivot. An example is a fisherman's rod. Levers are simple machines used to lift heavy loads with minimal effort. The load refers to the weight being lifted and the effort refers to the force applied to lift the weight.