Final answer:
When an elevator first starts moving upward, the scale reading is greater than a person's actual weight due to the force needed for acceleration. Once the elevator reaches a constant upward velocity, the scale reading will show the actual weight since there is no additional force needed.
Step-by-step explanation:
When an elevator first begins to move upward, the scale reading would be greater than the person's actual weight. This occurs because the scale must exert an upward force greater than the person's weight to accelerate them upward, in accordance with Newton's second law of motion. The faster the elevator accelerates, the greater the force exerted by the scale, which translates into a higher reading on the scale. Therefore, in the case of a man weighing 735 N standing on a scale in an elevator that accelerates upward at 1.20 m/s², the scale would show a weight greater than 735 N.
However, when the elevator reaches a steady state of constant upward velocity, the scale reading would return to the actual weight of the person (735 N in the example provided). At constant velocity, there's no acceleration, hence no additional force is required beyond what's necessary to counteract gravity. This is why you feel heavier when an elevator starts moving upward, but that sensation disappears once the elevator moves upward at a constant speed.