McHenry Forum - Crash Reconstruction & Simulation

On a recent zoom meeting many were using the term MU and so realized we hadn't added a 'What is' topic on it.
Q: What is MU?

A: MU is a term used for the coefficient of Friction.
Now you may ask:
What is the coefficient of Friction?

• The coefficient of friction (fr) is a number that is the ratio of the resistive force of friction (Fr) divided by the normal or perpendicular force (N) pushing the objects together. It is represented by the equation: fr = Fr/N.

This diagram also explains it:

• Which is from the video Physics 4.6 Friction (2 of 14) What is Coefficient of Friction?

IN the field of crash reconstruction we use MU frequently and here are a few threads with discussions of values for MU for various situations:

• Drag factors for metal on concrete and sand?
• Coefficient of friction of soft soils?
• Friction decrement at high speeds?
• Is there a tire friction variation in cooler temperatures?
• Friction tests of Studded Tires in Snow and Ice
• Friction Tests on Contaminated Surfaces
• Friction coefficient of grass