β¬οΈ Free Fall Calculator
Calculate fall time and impact velocity. No air resistance assumed.
How to Use This Calculator
Select what you want to solve for, then enter either the drop height or the fall time. The calculator returns fall time, impact velocity in m/s and km/h, and the height. Change the g value to model free fall on other planets: 1.62 m/sΒ² for the Moon, 3.72 m/sΒ² for Mars, 9.81 m/sΒ² for Earth.
Choose your mode from the dropdown. "Time and Velocity from height" is the most common: you know how far something falls and want to know how long it takes.
Enter the height in metres. This is the vertical distance fallen, measured from the starting point to the landing point.
Adjust g if needed. Earth standard is 9.81 m/sΒ². For a Moon problem, change this to 1.62.
Read the results. Impact velocity is shown in both m/s and km/h so you can get an intuitive feel for the speed.
Free Fall Equations
All objects fall at the same rate in free fall regardless of mass. A 1 kg ball and a 10 kg ball dropped from the same height will hit the ground at exactly the same moment (ignoring air resistance). This was famously demonstrated by Galileo and confirmed on the Moon by astronaut David Scott in 1971 with a hammer and a feather.
Worked Examples
Where This Comes Up in Real Life
Free fall calculations are used to estimate the danger of falling objects on construction sites. A 1 kg tool dropped from 20 m hits at about v = β(2 Γ 9.81 Γ 20) = 19.8 m/s, which is over 71 km/h. That is why hard-hat zones are mandatory. Engineers use this same formula when designing safety nets and calculating clearance distances around elevated work platforms.
Stunt performers and skydiving instructors use free fall equations to time when to open parachutes. In the first few seconds before air resistance becomes significant, the free fall formula is quite accurate. For a skydiver jumping from 4000 m, the first 5 seconds of free fall covers about 123 m, during which speed builds to roughly 49 m/s before drag forces become appreciable.
Frequently Asked Questions
What is free fall?
Free fall is motion under gravity alone with no air resistance. All objects fall at the same rate regardless of mass.
How long to fall 100 m?
t = β(2h/g) = β(200/9.81) β 4.52 seconds. Impact velocity β 44.3 m/s β 159 km/h.
Does mass affect fall time?
No β in the absence of air resistance, all objects fall at the same rate (Galileo's experiment).
What is terminal velocity?
When air resistance equals gravitational force, acceleration stops. This calculator assumes no air resistance.
What is g on other planets?
Moon: 1.62 m/sΒ², Mars: 3.72 m/sΒ², Jupiter: 24.79 m/sΒ². Change the g field to calculate for other planets.