Final answer:
To select a freight elevator, calculations must determine the work done by workers to move a crate with a constant velocity on different surfaces, not including the gravitational work done by the elevator.
Step-by-step explanation:
Before selecting a freight elevator, one must complete an analysis that includes the work needed by the workers to move an object along a specific path, which involves calculating the work done against frictional forces. In the case of moving a 200 kg crate, the work is determined by the distance the crate is moved, the coefficient of kinetic friction of the surfaces, and whether the crate is moved with constant velocity (meaning there is no acceleration). Since the workers are not responsible for doing the work against the force of gravity when using the elevator, this is not included in their calculations.
When sliding the crate at a constant velocity, the net force on the crate is zero, hence there is no acceleration, and the work done by the workers is equal to the force of friction times the distance moved on each floor. The work needed by the workers to bring the crate from the ground floor to the third floor using the elevator depends on the direction of the elevator's motion and acceleration. If the elevator is accelerating upward, then the work done by the workers is zero as the force provided by the elevator is opposing the force of gravity.