Question
Why does a stone fall faster than a feather when dropped from the same height? And if gravity pulls everything equally, why does this happen?
This is one of those questions that seems obvious until you actually think about it — and then it becomes fascinating.
Solution — Step by Step
Gravity pulls every object toward the Earth with an acceleration of g = 9.8 m/s², regardless of mass. A 5 kg stone and a 5 gram feather both experience the same downward acceleration due to gravity. This is Newton’s law of gravitation combined with his second law — the heavier object has more gravitational force on it, but also more inertia, and these cancel out perfectly.
Air resistance (drag force) depends on the shape, size, and speed of an object — not its mass. A feather has a large surface area relative to its weight, so air pushes back against it significantly. The stone, dense and compact, cuts through air with much less resistance relative to its weight. This is why the feather drifts down slowly — it reaches a low “terminal velocity” quickly.
When we remove air from the equation, everything changes. In a vacuum tube, a feather and a coin dropped simultaneously hit the bottom at exactly the same time. NASA famously demonstrated this on the Moon — astronaut David Scott dropped a hammer and a feather in 1971, and both landed together. The Moon has no atmosphere, so there’s no air resistance to interfere.
Galileo, without any vacuum chamber, reasoned his way to the correct answer. He asked: if heavier objects fell faster, what happens when you tie a heavy stone and a light stone together? The light stone should slow down the heavy one, but the combined object is heavier than either — so it should fall faster than the heavy stone alone. Contradiction. Therefore, mass cannot determine fall speed.
Net force on a falling object:
For the stone: is small relative to , so acceleration ≈ g.
For the feather: is comparable to , so net force is small → acceleration much less than g.
In vacuum: for both → both accelerate at exactly g = 9.8 m/s².
Why This Works
The key insight is separating two different things that air conflates: the gravitational effect (which treats all masses equally) and the aerodynamic effect (which treats objects based on shape and size). We live in air, so we only ever see the combined result — which tricks us into thinking heavy objects “fall faster” as a universal truth.
Galileo’s genius was recognising that our everyday experience was contaminated by air resistance, and that the “pure” physics of gravity was hidden underneath. This is exactly the kind of thinking that separates good physics students from excellent ones: always ask “what if I remove this complication?”
For your Class 9 board exam, the key statement to remember is: in the absence of air resistance, all objects fall with the same acceleration g, irrespective of their mass. This comes directly from NCERT Chapter 10 and appears in short-answer questions almost every year.
Alternative Method — Using Terminal Velocity
Instead of thinking about acceleration, we can think about terminal velocity — the constant speed an object reaches when drag equals gravity.
Here, = mass, = air density, = drag coefficient, = cross-sectional area.
For the feather: small , large → very small (it floats down slowly).
For the stone: large , small → large (it hits the ground fast).
This formula isn’t on your NCERT syllabus, but understanding the logic — that terminal velocity depends on the ratio of mass to surface area — is excellent conceptual clarity for MCQs.
Common Mistake
“Heavier objects always fall faster” — Students write this as a general law, which is wrong. It’s only true in the presence of air resistance and only when the air drag is significant. In a vacuum, mass makes zero difference to falling speed. If your answer says “heavier objects fall faster because gravity pulls them more,” you’ll lose marks because this reasoning is fundamentally incorrect — the extra gravitational pull is exactly cancelled by the extra inertia.
The two-line answer that always gets full marks in Class 9 boards: “In the presence of air resistance, a stone falls faster because its weight is much larger than air drag, while a feather’s weight is comparable to air drag. In a vacuum, both fall at the same rate with acceleration g = 9.8 m/s².”