Physics
Gravity
Drop a feather and a hammer in vacuum, on Earth, the Moon or Mars — and see why heavy objects don't fall faster.
World
Stats
- Time
- 0.00s
- Gravity
- 9.81 m/s²
- v feather
- 0.0 m/s
- v hammer
- 0.0 m/s
In a vacuum or on the Moon (no atmosphere) the feather and the hammer land at the same time. Add air, and the feather lags. Apollo 15's David Scott did this on live TV in 1971.
Newton watched an apple fall and asked the right question: if the same force pulls down apples *and* keeps the Moon in orbit, what does that force look like? One equation answered both.
Every mass attracts every other mass. On Earth's surface, gravity pulls things downward at about 9.8 m/s² — meaning each second, a falling object's downward speed increases by 9.8 m/s.
Satellites, GPS timing, planetary orbits, tides, falling objects, terminal velocity, even the way galaxies cluster — gravity rules every scale from the kitchen floor to the cosmos.
g ≈ 9.8 m/s² on Earth
G ≈ 6.674 × 10⁻¹¹ N·m²/kg². Force gets 4× weaker when distance doubles — inverse square.
How long does it take a stone dropped from rest to reach 20 m/s?
In a vacuum, a feather and a hammer fall at the same rate. The Apollo 15 astronauts demonstrated this on the Moon.
Mass and weight are different. Mass (kg) is how much stuff you have — same on the Moon. Weight (N) is the *force* gravity pulls with — much less on the Moon, because g is smaller.
- Gravity accelerates falling objects at g ≈ 9.8 m/s² near Earth's surface.
- Newton's law: F = G·m₁m₂/r² — inverse-square with distance.
- Mass is constant; weight depends on local gravity.