PHYSICS · Multi-part · A Level · Physics · Turning points in physics · Turning points in physics
Problem
A physicist steps into a sealed, windowless elevator car carrying a bathroom scale and two identical steel balls. The elevator car can move vertically but provides no outside view or audible cues. While inside, the physicist performs several simple observations.
• She places one ball on the scale and records the scale reading.
• She drops the second ball from shoulder height and times its fall to the floor.
• She compares the sound of her footsteps while walking across the cabin to what she normally hears in a stationary elevator on Earth.
Answer the following, assuming air resistance inside the cabin is negligible.
(a) Describe how each of the three observations listed would appear to the physicist if the elevator is actually at rest on Earth’s surface.
(b) Describe how the same three observations would appear if, instead, the elevator is located far from any massive body but is moving upward with a constant acceleration of 9.8m/s2.
(c) Provide a qualitative explanation for why the physicist cannot, based solely on these observations, determine which of the two situations in parts (a) and (b) she is experiencing.
(d) Propose an additional experiment that she could attempt inside the cabin. Explain carefully whether or not the outcome of that experiment would allow her to distinguish between the two situations, and justify your reasoning.