Calculator inputs
Example data table
These examples use standard gravity, zero initial velocity, and stopping distance mode.
| Scenario | Mass (kg) | Drop Height (m) | Stopping Distance (m) | Impact Speed (m/s) | Average Contact Force (N) |
|---|---|---|---|---|---|
| Phone on carpet | 0.22 | 1.00 | 0.015 | 4.43 | 146.04 |
| Toolbox on concrete | 10.00 | 0.75 | 0.005 | 3.84 | 14,813.10 |
| Parcel with foam insert | 5.00 | 1.50 | 0.040 | 5.42 | 1,888.43 |
| Helmet drop test | 1.40 | 2.00 | 0.030 | 6.26 | 929.33 |
Formula used
1) Impact velocity before contact
v = √(v₀² + 2gh)
Here, v₀ is initial downward velocity, g is gravity, and h is drop height.
2) Kinetic energy at impact
KE = ½mv²
This is the energy that must be absorbed during the stopping phase.
3) Average stopping deceleration using distance
a = v² / (2s)
Use this when you know how much the object compresses, crushes, or deforms while stopping.
4) Average stopping deceleration using time
a = v / t
Use this when you know the impact lasts a certain time instead of a known stopping distance.
5) Dynamic force and contact force
Dynamic force = ma
Average contact force = m(a + g)
The contact force includes both stopping deceleration and the weight contribution.
6) Rebound estimates
vᵣ = ev
hᵣ = vᵣ² / (2g)
The coefficient of restitution e estimates bounce velocity and rebound height.
How to use this calculator
- Enter the object mass and choose the correct mass unit.
- Enter the free-fall height and any initial downward velocity.
- Set gravity. Use 9.81 m/s² for Earth unless you need another environment.
- Choose either stopping distance or stopping time.
- Add a coefficient of restitution if bounce matters.
- Choose output units for force and energy.
- Click the calculate button to show the result under the header and above the form.
- Download CSV or PDF if you need a shareable record.
Frequently asked questions
1) What does this calculator actually estimate?
It estimates impact velocity, stopping deceleration, dynamic force, average contact force, rebound, impulse, and a peak force approximation from a chosen shock factor.
2) Why does stopping distance matter so much?
A longer stopping distance spreads the same impact energy over more motion, which reduces deceleration and lowers the average force dramatically.
3) Is the displayed force a true peak impact force?
No. The main result is an average contact force during stopping. True shock peaks can be higher, so the peak factor gives a practical engineering-style estimate.
4) Should I use stopping time or stopping distance?
Use distance when you know compression, crush depth, or deformation. Use time when you know contact duration from test data, sensors, or high-speed video.
5) What does the coefficient of restitution change?
It changes rebound velocity and rebound height. It also affects impulse because a bounce reverses direction, increasing the total momentum change during impact.
6) Can this help with packaging or drop testing?
Yes. It is useful for packaging, product drops, basic landing analysis, material cushioning comparisons, and early design checks before detailed simulations.
7) Why is there both dynamic force and contact force?
Dynamic force is only the stopping part, ma. Contact force adds weight, m(a + g), which is often more useful when sizing supports or estimating reaction loads.
8) Why does the graph rise sharply at small values?
Very short stopping distances or times require extreme deceleration. Because force depends directly on deceleration, small changes near zero can create very large force increases.