How does friction work quantitatively?

Post Reply
thegeneralsolution
Posts: 16
Joined: Sun Jul 05, 2015 12:55 am

How does friction work quantitatively?

Post by thegeneralsolution »

So I have a cube shaped rigid body sitting on a flat static collision object.

If I explicitly set the velocity to a constant at each frame, the object slides across the floor. The distance the object moves each frame is slightly less than velocity*frame_duration because of friction. No surprise there.

What I don't understand is how exactly that distance is reduced by the friction, quantitatively.

Let D be the difference between (velocity*time_duration) and the actual distance the object travels per frame (slowed by friction).

My observations (assuming I remember all my experiments correctly):

1. d does not depend on the mass or velocity of the object.
2. d DOES depend on the frame rate, and the gravity vector.
3. If you multiply the coefficient of friction of the object (or the floor) by k, then d is scaled by k.

With bullet's default settings (1/60 hz frame rate), gravity = (0,-1000,0), and both coefficients of friction at 0.5,
the velocity of the object is reduced by about D= 0.0696 per frame.

Is there a simple formula for D?

Thank you so much!
Post Reply