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## Slide Calculator

### This calculator determines the initial speed of a vehicle or other object that is sliding across a surface.

The ending velocity is the speed that the object was traveling when it has finished sliding across this surface. For example, the ending velocity of a vehicle that skids 50 feet and then strikes a barrier at 25 feet per second would be 25. The distance would then be 50. The slide distance is most often obtained by measuring the length of the skid marks or other marks on teh roadway. The drag factor is the ratio of the amount of force needed to drag the object horizontally across the surface, to the verticle weight of the vehicle. This information can be obtained using a drag sled or accelerometer. Sometimes it is not feasible to obtain the drag factor through impiricle testing. Therefore published data based on previous testing is sometimes used. For example, published data from Northwestern University suggests a drag factor of .55 to .80 for traveled asphalt and .60 to .80 for traveled concrete. This data assumes a level surface and must be adjusted for grade. This is done by simply adding the grade if the object is sliding up hill, or subtracting the grade if it is sliding downhill. 