Final answer:
An ergometer measures actual work output in joules (J).
Step-by-step explanation:
The actual work output measured by an ergometer is typically expressed in joules (J). One joule is the unit of work and energy in the SI system, and it is equal to a newton-meter (Nm). This means that if a force of one newton is applied to an object and it moves a distance of one meter in the direction of the force, the work done on the object is one joule.