Two solid spheres—one of lead and one of aluminum—have different masses but identical…
PHYSICS · Single correct · A Level · Physics · Mechanics and materials · Mechanics and materials
Problem
Two solid spheres—one of lead and one of aluminum—have different masses but identical radii. They are released simultaneously from rest in a tall evacuated chamber near Earth’s surface. Which of the following best explains why they reach the floor at the same time?
(a) Earth’s gravity exerts the same downward force on every object at a given location, so both spheres experience identical forces and fall together.
(b) Because the spheres have the same radius, their surface areas are equal; this makes the ratio of weight to area the same, giving them equal downward acceleration.
(c) For every object, the gravitational force Fg is directly proportional to its inertial mass m, so the ratio Fg/m equals the constant g for all materials, giving the same acceleration.
(d) Any difference in falling speed caused by mass would require a much taller drop; over the short height of the chamber the effect is negligible, so the spheres land at the same time.