Critical Speed Yaw Mark
Definition
Curved scuff marks deposited when a vehicle slides sideways. The radius of curvature and friction coefficient yield the vehicle's minimum speed at that point using the critical speed formula v = sqrt(r × g × mu).
- Appearance
- Curved scuff marks from sideways sliding
- Formula
- v = sqrt(r x g x mu)
- Output
- Minimum speed at that point
- Requires
- Radius of curvature and friction coefficient
Common questions
Why does the formula give a minimum speed rather than the exact speed at that point?+
The critical speed formula assumes the vehicle was at the point of sliding equilibrium, so it calculates the slowest speed at which that curvature could occur; the vehicle could have been travelling faster with additional braking or steering input.
Where along a yaw mark is the radius of curvature typically measured?+
Reconstructionists usually take a chord and middle ordinate measurement over a consistent segment of the curved mark, since radius can vary along the mark's length as the vehicle's slide angle changes.
Related terms
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- Skid Mark
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