Answer:
If you are standing on a scale in an elevator and suddenly notice that your weight decreases, it means that the elevator is accelerating downwards. When the elevator accelerates downwards, there is a decrease in the normal force acting on you, which is the force that the scale measures as your weight.
According to Newton's second law of motion, the net force acting on an object is equal to its mass times its acceleration. In this case, the net force acting on you is the force of gravity pulling you downwards minus the normal force pushing you upwards. When the elevator accelerates downwards, the normal force acting on you decreases, and therefore the net force acting on you decreases as well. Since your mass remains constant, a decrease in net force results in a decrease in acceleration, which is what the scale measures as a decrease in your weight.
Therefore, if you notice your weight decreasing while standing on a scale in an elevator, you can conclude that the elevator is accelerating downwards.
Step-by-step explanation: