Formula Used
Fall time: t = (−v₀ + √(v₀² + 2gh)) / g
Kinetic energy: E = ½mv²
Momentum: p = mv
Distance-based average force: F = mv² / (2d)
Duration-based average force: F = mΔv / Δt
Deceleration: a = v² / (2d)
Rebound speed: vᵣ = ev
Peak force estimate: Fₚ = K × Favg
The calculator applies force equations to the velocity component normal to the impact surface. When drag is enabled, it numerically integrates quadratic drag and buoyancy. Actual peak force requires a measured force-time curve or a validated structural model.
How to Use This Calculator
- Enter the object's mass, drop height, and initial vertical velocity.
- Select gravity or enter a custom gravitational acceleration.
- Enter stopping distance, impact duration, or both.
- Set rebound, impact angle, energy absorption, and safety values.
- Enable drag, fluid, spring, damping, or multi-stage options when needed.
- Select output units, calculate, then review warnings and charts.
- Export the result as CSV or use Print / PDF for a report.
Example Data
| Scenario | Mass | Height | Stopping distance | Impact duration | Use |
|---|---|---|---|---|---|
| Tool onto rubber mat | 5 kg | 2 m | 30 mm | 20 ms | |
| Package onto foam | 12 kg | 1.2 m | 80 mm | 45 ms | |
| Component onto hard floor | 2 kg | 0.8 m | 2 mm | 3 ms |
Saved Scenario History
| Date | Mass | Height | Velocity | Peak force | Status |
|---|---|---|---|---|---|
| No saved calculations yet. | |||||
Important Assumptions and Limitations
Impact force depends strongly on deformation, stiffness, damping, contact duration, geometry, material yielding, and force-time shape. A single average-force value cannot fully describe a complex collision. Preset surface values are illustrative and should not be treated as certified material properties.
Human injury, fall arrest, vehicle crash, lifting, structural, and protective-equipment decisions require applicable standards and qualified review. Use measured test data whenever consequences are significant. Never use this page as the only basis for life-safety decisions.
Frequently Asked Questions
Why does stopping distance change impact force so much?
The same kinetic energy must be removed. A longer stopping distance spreads that energy over more motion, reducing average force.
Is impact force equal to the object's weight?
No. Weight is the steady gravitational force. Impact force can be many times larger because velocity changes quickly.
Which estimate should I use, distance or duration?
Use the input supported by reliable data. If both are available, compare them and investigate large differences.
What is the peak-force multiplier?
It converts an average estimate into an approximate peak. Real multipliers depend on the force-time curve and structure.
What does coefficient of restitution mean?
It describes rebound. Zero means no rebound, while one represents an ideal elastic rebound along the normal direction.
When should air resistance be enabled?
Enable it for large areas, light objects, long falls, high speeds, or motion through dense fluids.
Can this calculator model an underwater fall?
Yes, enter the fluid density and displaced object volume. The model includes quadratic drag and buoyancy.
Why can force approach infinity?
An ideal zero stopping distance or zero stopping time demands an instantaneous velocity change. Real materials always deform.
What is design force?
Design force is the estimated peak force multiplied by the selected safety factor.
Can results replace testing or engineering analysis?
No. Complex impacts require validated models, standards, material data, instrumentation, or professional analysis.