A student first stands on a calibrated spring scale at sea level and then rides a…
PHYSICS · Multi-part · A Level · Physics · Fields and their consequences · Fields and their consequences
Problem
A student first stands on a calibrated spring scale at sea level and then rides a high-altitude balloon to a height equal to 1.0 percent of Earth’s radius above sea level. The mass of the student is 65 kg. Assume Earth is a uniform sphere, neglect air resistance, and ignore any effects due to Earth’s rotation.
(a) Qualitatively predict whether the scale reading at the balloon’s maximum altitude will be greater than, less than, or equal to the reading at sea level. State your reasoning without using numerical calculations.
(b) Using proportional reasoning, determine the approximate percentage change in the scale reading that results from ascending to a height equal to 1.0 percent of Earth’s radius. Show your reasoning clearly, but you do not need to carry out a full numerical calculation with constants.
(c) Astronauts in low-Earth orbit often describe themselves as "weightless." Using your answer to part (b) and appropriate physical reasoning, explain why astronauts feel weightless even though a substantial gravitational force still acts on them.