Work is the product of the force exerted on an object and the objects displacement due to the force. Work = force time distance. The multiplying the force applied to an object by the distance the object moves in the direction of the force. Since objects tend to continue moving after a force is applied, the distance is only measured while that force is being applied a simple machine has no source of energy except the immediate forces you apply. The only way to get output work on the machine. The output work done by a simple machine an never exceed the input work done on the machine, a screw is the simple machine that requires the least amount of work. The reason for that is the amount of force you apply does not take us much as the other simple machines.

Simple Machines