Name: _______________________ Date: __________
Measuring Coefficient of Friction
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Friction plays an essential role in the operation of all motor vehicles, both in providing
the force necessary to brake and in making turning possible. Since one of the most
important outcomes of accident reconstruction is determining the speed of the car,
knowing the effects of friction on the motion of the car is absolutely necessary.
In this lab, we will use a drag sled to measure the coefficient of friction (also called “drag
factor” in police lingo) of tires with various road conditions.
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Hypothesis
Before you begin making measurements, do you have any predictions about how or if the
coefficient of friction between the tires and the road will vary with the conditions?
Procedure
Part 1: Drag Factor
Choose a drag sled to use throughout the experiment (note that each sled features a
different grade of tire). At each station, record the road condition and measure the force
necessary to pull the cart along the ground at a slow, constant speed (meaning Fpull = Ff)
using the spring scale. Conduct three trials at each station.
The drag sled should be set up as follows:
