Braking Distance

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Equation / Last modified by KurtHeckman on 2018/01/04 17:04
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EmilyB.Braking Distance
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The Braking Distance calculator computes the distance to stop a vehicle based on the initial velocity (vi) and the a braking coefficient (μ).

Compute the Braking Distance

  1. Choose units (default: kilometer per hour)
  2. Enter the initial velocity (vi)
  3. Enter the Braking Coefficient (μ)

Braking Distance (BD):  The calculator returns the distance (BD) in meters.  However this can be automatically converted to other distance units via the pull-down menu.

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The Math / Science

The Braking distance refers to the distance a vehicle will travel when its brakes are fully applied to when it comes to a complete stop. It is primarily affected by the original speed of the vehicle and the coefficient of friction between the tires and the roads surface, and negligibly by the tires rolling resistance and vehicle's air drag. The type of brake system in use only affects trucks and large mass vehicles, which cannot supply enough force to match the static frictional force. 

The breaking distance is one of two components of total stopping distance. The following formula is used to calculate the braking distance:

     `BD=v_i^2/(2mug)`

where:

Braking Coefficient

The Braking Coefficient is a coefficient of kinetic friction.  For accident reconstruction on dry surfaces, a value of 0.7 is often used.  This is the default value in this calculator.  A modern car with computerized anti-skid brakes may have a friction coefficient of 0.9 - or even far exceed 1.0 with sticky tires. 

References

Formula and definition are from Wikipedia (https://en.wikipedia.org/wiki/Braking_distance).