Final answer:
The area that can be conveniently reached with a sweep of the forearm is called the Semi-Sweep Area.
Step-by-step explanation:
The area that can be conveniently reached with a sweep of the forearm while the upper arm is hanging in a natural position at the side is called the Semi-Sweep Area. The Semi-Sweep Area refers to the space that can be easily accessed without having to stretch or strain the arm excessively. This concept is particularly relevant when designing horizontal work surfaces to promote ergonomic and efficient movements.