Example data table
These examples are computed using the same model and assumptions as this calculator.
| Mass (kg) | Speed (mph) | Angle (°) | e | Crush (m) | Glancing | Absorbed Energy (kJ) | Avg Force (kN) | Avg Decel (g) |
|---|---|---|---|---|---|---|---|---|
| 1500 | 32 | 0 | 0.15 | 0.45 | 0 | 150 | 341.1 | 23.2 |
| 1500 | 32 | 25 | 0.15 | 0.45 | 0 | 123 | 280.2 | 19.0 |
| 1800 | 40 | 0 | 0.1 | 0.55 | 0 | 285 | 523.2 | 29.6 |
| 1300 | 25 | 35 | 0.2 | 0.4 | 0.05 | 50 | 136.2 | 10.7 |
| 1600 | 30 | 15 | 0.25 | 0.35 | 0.05 | 120 | 383.6 | 24.4 |
| 2000 | 45 | 10 | 0.12 | 0.6 | 0.1 | 348 | 654.1 | 33.4 |
| 1200 | 20 | 0 | 0.3 | 0.3 | 0 | 44 | 159.9 | 13.6 |
| 1700 | 35 | 45 | 0.15 | 0.5 | 0.1 | 92 | 208.1 | 12.5 |
Formulas used
- Total kinetic energy: E = ½ m v²
- Normal speed component: vₙ = v · cos(θ) (θ is degrees from perpendicular)
- Normal-component energy: Eₙ = ½ m vₙ²
- Absorbed energy (rigid pole model): E_abs ≈ (1 − e²) · Eₙ
- Average deceleration (work-energy): a_avg ≈ vₙ² / (2 d)
- Average force: F_avg ≈ m · a_avg
- Average pressure (rough): P_avg ≈ F_avg / A
How to use this calculator
- Enter vehicle mass and impact speed using your preferred units.
- Set the impact angle from perpendicular (0° is straight into the pole).
- Choose a restitution value to model rebound versus absorption.
- Provide a crush distance to estimate force and deceleration.
- Optionally add glancing reduction, pole diameter, and contact height.
- Click Calculate, then export CSV or PDF if needed.
This short reference explains what the calculator outputs mean and how the inputs affect the result. Values are simplified to help comparisons between scenarios. For design, testing, or crash reconstruction, always cross-check with measured crash pulses and validated vehicle models.
1) Side pole impact energy in one number
The tool starts from vehicle kinetic energy and focuses on the normal component of a pole strike. A 1,500 kg vehicle at 32 km/h has ~59 kJ total energy; at 15° the normal energy is slightly lower, so the effective “hit” is reduced versus a straight impact.
2) Mass and speed dominate the result
Energy scales linearly with mass and with the square of speed. Doubling mass doubles energy, but doubling speed multiplies energy by four. Even small speed increases matter: 40 km/h carries far more energy than 32 km/h at the same mass.
3) Angle converts speed into a normal component
Side pole impacts are often oblique. The calculator uses vₓ = v cos(θ) to compute normal speed and Eₓ = ½ m vₓ² for normal energy. Tangential speed mostly produces sliding and rotation rather than crush work.
4) Restitution estimates rebound vs absorption
Restitution (0 to 1) approximates how much normal speed remains after contact. Absorbed energy is estimated as Eabs = (1-e²) Eₓ. Lower e means more energy must be dissipated through deformation, friction, and heat.
5) Crush distance turns energy into average force
With a crush distance d, average force is Favg = Eabs/d. Example: 90 kJ absorbed over 0.35 m gives ~257 kN. Halving d roughly doubles average force.
6) Average deceleration provides a severity check
Average deceleration follows aavg = Favg/m and is shown in g. Using 257 kN on 1,500 kg gives ~171 m/s² or ~17.4 g. Real pulses vary in time, so use this as a comparison metric, not a peak.
7) Contact area and stiffness add context
If you enter pole diameter and contact height, the tool estimates contact area and a pressure proxy P̄ ≈ Favg/A. A 254 mm pole with 0.30 m contact height implies ~0.076 m² contact area, suggesting a more localized load for the same force.
FAQs
1) What does restitution mean in this calculator?
It is a rebound factor for the pole-normal direction. A value of 0 assumes no rebound (maximum absorption). Higher values keep more post-impact normal speed, reducing absorbed energy.
2) Why does the angle reduce the energy so much?
Only the speed component perpendicular to the pole produces crush work. The tangential component mostly causes sliding and rotation. The normal speed is computed using cosine of the impact angle.
3) Is the average force the same as peak force?
No. The calculator estimates an average force from absorbed energy and crush distance. Real crashes have a force pulse with peaks and valleys, so peak force can be higher than the average.
4) What crush distance should I enter?
Use a best estimate of the effective deformation distance along the impact direction. For quick checks, 0.20–0.60 m is common in moderate-to-severe events, but it varies widely by vehicle structure and impact location.
5) Why do I see both kJ and ft·lbf?
They are the same energy expressed in different unit systems. kJ is standard in engineering and testing, while ft·lbf is common in some field reports. Conversions are handled automatically.
6) Can I use this for safety ratings or legal conclusions?
Use it for education, estimates, and scenario comparison. Safety ratings rely on instrumented crash tests and injury metrics, and legal conclusions require expert analysis with verified inputs and documented methods.