A passenger stands barefoot on a bathroom scale inside an elevator that starts from rest at the ground floor, moves upward, and later descends. The elevator’s motion consists of the following consecutive intervals.
• Interval I (0–3 s): elevator accelerates upward at a constant magnitude.
• Interval II (3–10 s): elevator moves upward at constant speed.
• Interval III (10–13 s): elevator decelerates uniformly to rest at the top floor.
• Interval IV (13–16 s): elevator remains at rest with doors open.
• Interval V (16–19 s): elevator begins its descent, accelerating downward at a constant magnitude equal in size to the magnitude in Interval I.
Assume the passenger’s mass is m and the local gravitational field strength is g. Ignore air resistance and friction in the elevator mechanism.
(a) Describe qualitatively how the reading of the scale during Interval I compares with the passenger’s true weight mg. Explain your reasoning in terms of forces acting on the passenger.
(b) During Interval II, is the scale reading greater than, less than, or equal to mg? Justify your answer without performing numerical calculations.
(c) Explain why the scale reading changes during Interval III even though the elevator is still moving upward.
(d) Predict the scale reading during Interval V relative to mg and justify your prediction.