Advanced Crash Investigation Flashcards
A percentage of gravity that affects a vehicle’s ability to decelerate or accelerate.
Coefficient of friction
A term that denotes the sharpness of a curve, yawning mark or curb line.
Radius
A straight line measurement between two points on an arc that cannot be larger than the diameter.
Chord
Skid marks that start, stop and start again. Gaps are 8-10 feet.
Gap skid
The braking efficiency of a vehicle for front braking only.
60%
The normal split for the braking efficiency of a front engine vehicle, between the front and rear brakes.
60/40
The perpendicular measurement from the midpoint of a chord to the edge of an arc
Middle ordinate
Skid marks that are regularly and repeatedly interrupted by small gaps. Usually 8 - 10 inch gaps. Measure them from beginning to end as a straight skid.
Skip skid
A type of energy that is dissipated as a result of the distance an object moves.
Work
The correction made to the minimum speed formula to account for percentage of available factor.
Braking efficiency
A mark left by a tire that is rotating and sliding sideways
Yaw mark
A measurement between the centers of the axles of a vehicle
Wheelbase
The system that defines the order math functions must be performed in an equation
Mathematical order of operation
Term used to express the amount of rise or fall relationship to the run of the slope.
Grade
Determined by the force necessary to maintain constant movement of the object across the surface
Dynamic friction
A device used to determine the coefficient of friction of a surface
Drag sled
Determined at the moment the force overcomes the inertia of the object and starts to slide across the surface
Static friction
When determining the minimum speed from its skid mark, you should average the length of the skid marks
Minimum speed from skid marks
When working on a crash across surfaces with multiple drag factors, where do we begin?
Start at the end of the crash
When working with a crash across surfaces with multiple drag factors, which speed calculation will provide a true speed?
The speed calculation on the last surface before the vehicle stopped.
When working with a crash across surfaces with multiple drag factors, what can calculated speed values for the individual surfaces be useful for?
Kinetic energy calculations
A angle of less than 90 degrees
Acute angle
A combination of tangible and intangible points
Semi-tangible
The relationship between the opposite side and the hypotenuse of a right triangle.
Sine
Greater than a 90 degree angle
Obtuse angle
An angle of 90 degrees
Right triangle
Airborne equation used when an object launches and lands on the same plane.
Flip formula
Rate of acceleration due to gravity.
32.2 fps^2
Airborne equation used when an object is on a negative grade before launch.
Fall formula
A rough pencil sketch that identifies points to be measured at a collision scene
Field sketch
A perpendicular measurement from the midpoint of a chord to the edge of an arc.
Middle ordinate
Rate of motion expressed as miles per hour
Speed
The relationship between the adjacent side and the hypotenuse of a right triangle.
Cosine
A system of measurements that requires only one reference point
Coordinate system
A useful means of organizing the measurement data taken from a crash scene.
Data block
A method of locating a spot at a scene by measurements from two or more reference points
Triangulation method
Rate of motion expressed in feet per second
Velocity
A point that does not physically exist.
Intangible
Occurs when two straight lines meet at a point
Angle
A reference point that physically exists
Tangible reference point
Rate of change of velocity with respect to time.
Rate of acceleration
Which airborne formula is the most accurate?
Vault formula
Where is the center of mass for a pedestrian assumed to be?
At one-half the pedestrian’s height.
When should the Fall Formula not be used?
When Grade (G) is above 10% or take off angle is less than 6 degrees.
What is the one measurement that absolutely must be taken at a scene?
Drag factor
For investigative purposes, weight multiplied by the speed of the vehicle.
Momentum
Method used to determine speeds of vehicles at impact, based on post-impact speeds and weights.
Conservation of momentum
Used to determine braking distance on a skid test
Longest skid
Used to determine braking distance on a crash
Average skid
Grade above which you should not use the Fall Formula
10%
The angle above which you cannot use the Fall Formula
6 degrees
What to use for drag factor when the vehicles join as one at impact and less than all eight wheels are locked?
Effective Factor
