Weight at an altitude of one Earth radius
An astronaut weighs 900 N on Earth's surface. What does she weigh at an altitude equal to one Earth radius above the surface?
Answer B: explanation for every choice
A
This uses a distance of 3R from Earth's center instead of 2R.
B
Correct. Her distance from Earth's center doubles (R → 2R), so her weight is 900/2² = 225 N.
C
This uses 1/r instead of 1/r².
D
Weight decreases with distance from Earth's center.
TakeawayMeasure r from the planet's center, not the surface.
Equation usedNewton's law of gravitation
See your set score →Reviewed 2026-11-05 by a medical student. Spot an error? Report it with question ID cp148.