The force applied to a machine when it does work is known as the applied force.

Here's why:

* Work: In physics, work is defined as the force applied over a distance.

* Applied Force: This is the force that is directly responsible for causing the displacement or movement of the object.

* Machine: A machine is a device that multiplies or redirects force to make work easier.

So, when a machine performs work, it's the applied force that is directly responsible for causing the object to move and thus work being done.