What Is Free Fall?
Free fall is the motion of an object under the sole influence of gravity. In a vacuum, all objects — feathers, hammers, bowling balls — fall at exactly the same rate. This was famously demonstrated on the Moon by Apollo 15 astronaut David Scott.
On Earth, air resistance slows down light or large-surface-area objects. The equations here assume no air resistance (vacuum conditions), which is a good approximation for dense, compact objects over short distances.
Free Fall Formulas
These assume the object starts from rest (v₀ = 0) and falls a distance h. For objects thrown upward: max height = v₀²/(2g) and total flight time = 2v₀/g.
Gravity on Other Planets
| Body | g (m/s²) | 10 m fall time |
|---|---|---|
| Earth | 9.81 | 1.43 s |
| Moon | 1.62 | 3.51 s |
| Mars | 3.71 | 2.32 s |
| Jupiter | 24.79 | 0.90 s |
| Pluto | 0.62 | 5.68 s |
How to Use the Calculator
- Select the mode matching your problem.
- Enter height, time, or velocity. Optionally change gravity.
- Click Calculate.
- Review fall time, distance, velocity, and max height.
Example Calculations
10 m drop on Earth
t = √(20/9.81) = 1.43 s, v = 14.0 m/s
3 seconds of free fall
h = ½(9.81)(9) = 44.1 m
Throw up at 20 m/s
hₘₐₓ = 400/19.61 = 20.4 m, total time = 4.08 s
Common Mistakes
- Ignoring air resistance for low-density objects (feathers, parachutes).
- Using g = 10 m/s² when precision matters (g = 9.80665 m/s²).
- Forgetting that upward throw total time is twice the rise time.
- Confusing height with total path length for upward throws.
Accuracy and Limitations
These formulas assume vacuum conditions (no air resistance) and constant gravitational acceleration. Real falls are affected by air drag, altitude-dependent gravity, and object shape. Terminal velocity limits real-world fall speeds. For precise engineering, use computational fluid dynamics models.
FAQ
What is free fall?›
Free fall is motion under gravity alone, with no air resistance. In practice, a vacuum or near-vacuum is needed for true free fall.
Do heavier objects fall faster?›
No. In a vacuum, all objects fall at the same rate. Galileo demonstrated this concept. Air resistance makes lighter or less aerodynamic objects fall slower.
How fast does a falling object go?›
In free fall on Earth, speed increases by about 9.8 m/s every second. After 1 s: 9.8 m/s; after 2 s: 19.6 m/s; after 3 s: 29.4 m/s.
What is terminal velocity?›
Terminal velocity is the maximum speed an object reaches when air drag equals gravity. A skydiver reaches ~53 m/s (120 mph). This calculator does not account for air resistance.
How far does an object fall in 1 second?›
h = ½gt² = ½(9.81)(1)² = 4.9 m (about 16 feet) on Earth.
What is the gravity on the Moon?›
gₘₒₒₙ ≈ 1.62 m/s², about 1/6 of Earth’s gravity.
Can I use this for objects thrown upward?›
Yes. Use the Upward Throw mode to find maximum height and total flight time.
Sources
Author & technical reviewer
Manish Kumar
PhysicsCalcs tools are reviewed with an educational focus: clear formulas, transparent assumptions, and practical context for students and science learners.
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