Post-impact motion
Post-Impact Speed from Final Rest
Work backward from documented final-rest motion to estimate a vehicle's departure speed after impact.
Method overview
departure speed = √(sum of supported post-impact energy-loss terms)
The worksheet combines sliding or rolling segments using the conditions applicable to each segment. The resulting departure speed can support a later momentum calculation.
Evidence to document
- Impact-area and final-rest positions.
- Path length and direction for each motion segment.
- Drag factor, grade, and wheel condition for each segment.
- Rotation, curb strikes, terrain changes, or additional contacts.
Limitations
A straight-line slide model may not represent rotation, vaulting, wheel damage, curb impacts, or other discontinuous energy losses.
Record measurements, assumptions, units, rounding, and source material so another investigator can reproduce the result. See the methodology and validation center for verification policy and citation guidance.