Look at the wheelbarrow in the Figure below . It is used to carry heavy objects. It consists of two simple machines a lever and a wheel and axle. Effort is applied to the lever by picking up the handles of the wheelbarrow. The lever, in turn, applies upward force to the load. The force is increased by the lever, making the load easier to lift. Effort is applied to the wheel of the wheelbarrow by pushing it over the ground. The rolling wheel turns the axle and increases the force, making it easier to push the load.
The refrigerator was the last thing that mark needed to load onto the moving truck. He slid the edge of the dolly under the refrigerator and pushed down on the handle, lifting the refrigerator off the floor. He then pushed on he cart and rolled it out to the truck.
Is there one or multiple machines involved?