Book 23, Question 140
Why Does a Feather Fall More Slowly than a Coin?
Drop a feather and a coin. The feather drifts, the coin zooms. Why is one so much slower? In a vacuum or on the Moon, a feather and a coin fall at the same speed.
More fun facts
- On Earth, a hammer reaches the ground before a feather mostly because air pushes back harder on the light, fluffy feather.
- For the Apollo 15 test in 1971, the hammer was a 1.32 kilogram aluminum geology hammer and the feather came from a falcon.
- Both were let go from about 1.6 meters above the Moon's surface during the mission's last moonwalk.
- A NASA scientist pointed out that the trip home depended on the same physics the test was checking.
- Galileo tested the idea with two heavy balls of different masses, though many historians doubt the famous Leaning Tower of Pisa story.
- The rule that gravity speeds up every object the same way, no matter its mass or shape, is called the equivalence principle.
Questions kids ask
Would a feather and a coin fall together without air?
Yes. With no air to slow the feather, gravity speeds up both the same way.