What units are the physics material in?

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I have two spheres colliding. I'm trying to match the velocity profile (velocity decay due to friction) to a real-world collision. I have the values from dynamic friction and static friction from the real-world data in meters per second (m/s).

Are the dynamic frictions and static friction in the physics material settings in meters per second?

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Answer by PatientVoid · Jul 15, 2020 at 01:35 PM

Okay, answering my own question. Turns out, they are unitless values. So I'd have to convert the real world values to unitless values for them to match.

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Edy · Jul 16, 2020 at 12:00 PM 1

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Friction is coefficient of friction, "mu" (μ).

Personally, I have never seen friction expressed in m/s (which is a velocity). How can a velocity be interpreted as friction?

PatientVoid · Jul 16, 2020 at 12:25 PM 0

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@Edy The rate of change of velocity (acceleration) can be equated to mu times gravitational acceleration. I have the acceleration of a ball and the gravity constant, but missing mu. Therefore if I divide acceleration of ball with the acceleration of gravity, it'd equal to mu. The units cancel out and thus the coefficient of friction is unitless.

I was forgetting to divide by gravity and thus had mu *9.81m/s^-2, thus the units.

neonsloth21 · Mar 09 at 07:41 AM 0

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@Edy I think friction is typically in newtons in real world physics

Edy neonsloth21 · Mar 09 at 09:33 AM 0

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Friction force is Newtons. But coefficient of friction is a unitless value, "mu" (μ). Friction force (newtons) equals coefficient of friction (unitless) times normal force (newtons).

What units are the physics material in?

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