Final answer:
The force exerted by the bottom block on the top block in an upward-moving elevator is greater than the gravitational force on the top block to accelerate it upward. Once the elevator moves with a constant velocity, that force becomes equal to the top block's weight since no acceleration occurs.
Step-by-step explanation:
When an elevator is moving upward, particularly if it is accelerating, the force exerted by the bottom block (the scale) on the top block (the person or object being weighed) must be greater than the force of gravity (weight) of the top block. This additional force is necessary to accelerate the object upward, in addition to countering the force of gravity. This situation aligns with Newton's second law of motion, where the net force (Fnet) on an object is equal to the mass (m) of the object multiplied by its acceleration (a), Fnet = ma. When an elevator is moving upward with a constant velocity, the acceleration is zero (a = 0), meaning the force from the bottom block on the top block will be equal to the weight of the top block, as no additional force is needed beyond what is necessary to counteract gravity.