Final answer:
The scale measurement in an elevator measures weight, which is the force exerted by an object due to gravity. The scale reading will vary depending on the motion of the elevator.
Step-by-step explanation:
The scale measurement when stepping onto a scale in an elevator is measuring weight. Weight is the force exerted by an object due to gravity and is measured in units of Newton. When in an elevator, the scale reading will vary depending on the motion of the elevator.
When the elevator accelerates upward or moves upward at a constant speed, the scale reading will be equal to the person's weight because the force of gravity and the force of the elevator cancel each other out. However, if the elevator is in free fall or accelerating downward, the scale reading will be less than the person's weight because the force of gravity is reduced in those cases.