Does a heavier object fall faster than a lighter one?
Short answer: Free-fall acceleration is g for every mass; more weight is exactly balanced by more inertia.
The trap
The wrong idea
“In free fall (no air), a heavier object falls faster.”
It sounds reasonable, and a lot of JEE/NEET aspirants carry it into the exam. Here's a one-question check, then the explanation that makes it click.
Quick check
Try it before you peek
A 1 kg and a 10 kg ball are dropped together in vacuum from the same height. Which lands first?
- 10 kg ball
- 1 kg ball
- Both together
Show the answer
C. Both together
Free-fall acceleration is g for every mass; more weight is exactly balanced by more inertia.
The click
The intuition comes from everyday life, where air resistance matters: a feather drifts while a stone drops. Remove the air and the difference disappears.
Gravity does pull harder on a heavier object: the force is F = mg, so a 10 kg ball feels ten times the pull on a 1 kg ball. But the 10 kg ball also has ten times the inertia, so it is ten times harder to accelerate. Newton's second law gives a = F/m = mg/m = g. The mass cancels, and both balls accelerate at the same g ≈ 9.8 m/s².
Same acceleration, same starting speed (zero) and same height mean the same fall time: t = √(2h/g), which contains no mass at all. Dropped together in a vacuum, they land together. Astronaut David Scott showed this on the Moon during Apollo 15 in 1971, dropping a hammer and a feather that reached the ground at the same moment.
With air, the story changes because drag depends on an object's size, shape and speed, not on its mass. Of two balls the same size, the heavier one can reach a higher terminal speed, which is why it falls faster in air. That is an air effect, not a gravity effect. In "neglect air resistance" problems, mass never decides the free-fall time.
Got this one? The Knot Scan finds the misconception you don't know you have, in 8 questions.