🪂 Free Fall Calculator
Calculate free fall motion
Leave blank if entering time
Leave blank if entering height
How to Use This Calculator
Enter Height OR Time
Enter either the height (m) from which the object falls, OR the time (s) it takes to fall. You only need one - the calculator will compute the other. Leave the unused field empty.
Enter Gravity (Optional)
The default gravity is 9.81 m/s² (Earth's standard). You can change this for calculations on other planets or for precision. Moon = 1.62 m/s², Mars = 3.71 m/s².
Click Calculate
Press "Calculate" to find the missing value (height or time) and the final velocity upon impact.
Formula
h = ½gt²
t = √(2h/g)
v = gt
Where:
- h = Height/distance fallen (m)
- g = Acceleration due to gravity (9.81 m/s² on Earth)
- t = Time of fall (s)
- v = Final velocity (m/s)
Example Calculation:
An object falls from a height of 100 m:
1. Time: t = √(2 × 100 / 9.81) = √(20.39) = 4.52 s
2. Final velocity: v = 9.81 × 4.52 = 44.3 m/s (159.5 km/h)
About Free Fall Calculator
The Free Fall Calculator determines how long it takes for an object to fall a certain distance, or how far it falls in a given time, assuming it starts from rest and falls under the influence of gravity alone. This calculator assumes no air resistance, which is a good approximation for dense objects or short falls.
What is Free Fall?
Free fall is motion under the sole influence of gravity, with no air resistance or other forces. In free fall, all objects accelerate at the same rate regardless of mass - a principle famously demonstrated by Galileo. On Earth, this acceleration is approximately 9.81 m/s².
Key Principles
- Mass Independence: All objects fall at the same rate in vacuum, regardless of mass. A feather and hammer hit the ground simultaneously when dropped from the same height (in vacuum).
- Constant Acceleration: Gravity provides constant acceleration, so velocity increases linearly with time: v = gt.
- Quadratic Distance: Distance fallen increases with the square of time: h = ½gt². An object falls 4× farther in 2× the time.
- No Initial Velocity: This calculator assumes objects start from rest (vâ‚€ = 0).
Real-World Considerations
- Air Resistance: For light objects or high speeds, air resistance becomes significant. Use the Free Fall with Air Resistance calculator for more accurate results in those cases.
- Terminal Velocity: Falling objects reach terminal velocity when air resistance equals weight. Skydivers reach ~55 m/s (200 km/h) terminal velocity.
- Variable Gravity: Gravity varies slightly with altitude and location. At 10 km altitude, gravity is about 0.3% less than at sea level. For most calculations, 9.81 m/s² is sufficiently accurate.
Practical Applications
- Physics Education: Understand gravity and kinematics principles through hands-on calculations.
- Engineering: Calculate drop heights for safety testing, design impact protection systems, and determine fall times for construction safety.
- Sports: Estimate fall times for skydiving (before terminal velocity), bungee jumping, and cliff diving.
- Safety Planning: Calculate fall distances for workplace safety, window washer equipment, and fall protection systems.
Frequently Asked Questions
Why do all objects fall at the same rate?
In vacuum (no air resistance), all objects experience the same gravitational acceleration regardless of mass. Heavier objects have more weight (force), but also more mass to accelerate, so the acceleration (force/mass) is the same for all objects.
What about air resistance?
This calculator ignores air resistance, which is valid for dense, compact objects or short falls. For light objects (feathers, paper) or long falls where objects reach high speeds, air resistance significantly slows falling. Use the Free Fall with Air Resistance calculator for those cases.
How fast do objects actually fall on Earth?
After 1 second: 9.81 m/s (35 km/h). After 5 seconds: 49 m/s (176 km/h). After 10 seconds: 98 m/s (353 km/h). However, terminal velocity (usually 50-60 m/s for humans) limits maximum speed due to air resistance.
Can I use this for objects thrown upward?
This calculator is for objects dropped from rest. For objects thrown upward or downward with initial velocity, use the displacement calculator or projectile motion calculators.
Does gravity change with height?
Yes, but the change is small for practical purposes. At 10 km altitude, gravity is about 0.3% less than at sea level. For most calculations, 9.81 m/s² is sufficiently accurate.
What's the difference between this and free fall with air resistance?
This calculator assumes no air resistance (ideal case). The air resistance version accounts for drag force, which becomes significant for light objects or high speeds. Use the simpler version for dense objects or short falls, and the air resistance version for accurate long-fall calculations.