Input Parameters
Results
Enter the parameters above and click "Calculate impact force" to see results here.
| # | Mass (kg) | Height (m) | g (m/s²) | Impact time (s) | Stopping distance (m) | Velocity (m/s) | Force (time model) (N) | Force (distance model) (N) |
|---|
CSV export includes all calculations in the table above. PDF export uses your browser's print-to-PDF feature.
Example data table
The following examples illustrate typical ranges of parameters and resulting impact forces.
| Mass (kg) | Height (m) | g (m/s²) | Impact time (s) | Stopping distance (m) | Velocity (m/s) | Force (time model) (N) | Force (distance model) (N) |
|---|---|---|---|---|---|---|---|
| 10 | 2 | 9.81 | 0.05 | 0.10 | 6.26 | 1252.0 | 1962.0 |
| 75 | 0.5 | 9.81 | 0.30 | 0.25 | 3.13 | 783.1 | 1471.5 |
| 1000 | 1.5 | 9.81 | 0.10 | 0.20 | 5.42 | 54200.0 | 73575.0 |
Formula used
For an object in vertical free fall without air resistance, the impact velocity v after falling from height h under constant gravitational acceleration g is
v = √(2 · g · h)
The kinetic energy at impact is
E = ½ · m · v² = m · g · h
where m is the mass of the object.
Two average impact force models are used:
- Time-based model: assuming the object comes to rest in time Δt, the average impact force is
Favg,time = m · v / Δt. - Distance-based model: assuming the object stops over distance d, energy conservation gives
Favg,dist · d ≈ E, soFavg,dist = m · g · h / d.
These are simplified average values. Real impact forces depend on material properties, deformation, and detailed time variation of the contact force.
How to use this calculator
- Enter the object mass in kilograms.
- Specify the vertical drop height from the release point to the impact point.
- Optionally adjust gravitational acceleration if you are analysing another celestial body.
- Provide either the impact duration, the stopping distance, or both, depending on the data you have.
- Choose how many decimal places you want in the output.
- Click "Calculate impact force" to generate velocity, energy, and average impact forces.
- Review the numerical summary and the results table for comparison between different scenarios.
When you have several scenarios, export the table as CSV for further analysis in a spreadsheet or print the result card as a PDF report.
Free fall impact force overview
When a body falls freely, gravitational potential energy converts into kinetic energy. At the instant of impact, this energy is transferred to the surfaces in contact, creating potentially large forces over very short times or small stopping distances. Understanding this conversion is essential for safe design.
Relationship between height and impact velocity
Impact velocity depends on the square root of the drop height. Doubling the height does not simply double the velocity; instead, it increases by a factor of square root two, which already produces a significant increase in kinetic energy and impact force on structures, supports, and restraints.
Effect of mass on impact force
Mass scales both the weight force and the kinetic energy. Heavier objects carry more energy at the same height, so they can cause greater damage on impact. This calculator lets you quickly compare different masses while keeping all other parameters constant, highlighting how sensitive systems are to load changes.
Role of stopping time in impacts
For a given mass and velocity, a shorter stopping time means a larger average impact force. Very rigid collisions, such as metal on concrete, produce very small stopping times and therefore higher forces than softer, more cushioning surfaces that extend the contact time and reduce peak loads.
Role of stopping distance in impacts
Stopping distance provides another way to describe how quickly motion is arrested. Thick padding, deformable supports, or crumple zones increase stopping distance. A larger stopping distance spreads energy dissipation over a longer path, reducing the average impact force on structures, fasteners, occupants, and attached equipment.
Comparing time and distance models
The time and distance models are consistent if the motion during impact is approximately uniform deceleration. In practice, real force histories are irregular, yet these simple averages are very useful for initial sizing of supports, anchors, and protective materials during conceptual calculations and feasibility checks.
Engineering and safety applications
Engineers use free fall impact estimates when designing lifting systems, safety nets, fall arrest equipment, storage racks, and container drop tests. By exploring different heights, masses, and stopping characteristics with this calculator, you can evaluate risk levels and choose safer design margins before prototyping or laboratory testing.
Frequently asked questions
What assumptions does this impact force calculator make?
The calculator assumes vertical free fall without air resistance, constant gravitational acceleration, and average impact forces. Material behaviour, rotation, off-axis motion, and detailed force–time histories are not modelled, so results should be treated as approximate design values.
Can I use this tool for human fall safety assessments?
You can obtain approximate impact velocities and average forces, but human injury risk depends on many additional factors. Always consult safety standards, specialist guidelines, and qualified professionals before using any numerical results for personal protective equipment or workplace fall protection decisions.
How should I choose the impact duration value?
Impact duration is often estimated from experiments, high-speed video, or literature on similar materials. Softer, more deformable systems generally have longer contact times. When data is uncertain, it is common practice to evaluate several plausible durations to cover best- and worst-case scenarios.
Why are the time and distance forces different?
The two methods use different input descriptions: one is based on stopping time and the other on stopping distance. Measurement uncertainty, non-uniform deceleration, and energy losses not included in the simple model can cause noticeable differences between the two calculated average forces.
What units should I use for distance and time?
All distances, including height and stopping distance, must be in metres, while time values are expressed in seconds. Mixing unit systems will produce incorrect results, so always convert centimetres, millimetres, inches, or milliseconds into base SI units before performing calculations.
Can this calculator handle nonvertical or bouncing impacts?
The current implementation treats motion as purely vertical and assumes a single impact event. Oblique impacts, bouncing, multiple contacts, or sliding require more advanced dynamic models. You may still use the vertical component of velocity as a rough first approximation.