Final answer:
A machine with a mechanical advantage less than 1 increases the distance over which force must be applied, transforming the work done rather than reducing effort. This is useful for precise movements and is due to the conservation of energy, which mandates that a machine cannot create energy but only alter the application of force and distance.
Step-by-step explanation:
When a machine has a mechanical advantage less than 1, it means that the machine amplifies the distance over which a force is exerted rather than reducing the force required to do the work. This could be useful in situations where a precise or controlled movement is more important than reducing effort. An example is a lever where you exert a larger force over a shorter distance to move the opposite end of the lever a greater distance with less force. This might not make the work easier in terms of force exerted, but it could enable you to move something through a longer distance that you could not otherwise, or to position something very precisely.
The principle behind simple machines like the lever is the conservation of energy, which dictates that machines cannot create energy; they can only transform how it's applied. The work output of a machine cannot exceed the work input. The output force applied to the machine multiplied by the output distance is always equal to the input force multiplied by the input distance (Work = Force x Distance).
Even with a mechanical advantage less than one, the machine is altering the work by changing, in this case, the distance component rather than the force component. The result is that for any given task, you would need to apply the force over a longer distance to perform the same amount of work.