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Author Topic: microscope view of friction force (does not depends on macroscopic area)  (Read 10336 times)
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Fu-Kwun Hwang
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on: June 29, 2013, 06:20:50 pm » posted from:,,Satellite Provider

The following simulation try to illustrate why the friction force does not depends on macro-scopic area.
However, it does depends on microscope contact area.

The multiplication of width(w) and height(h) are kept constant. w*h=A=constant.

When the width is educed, the height increase (so the pressure increase).

A new function has been added: you can drag spring to change the external force acting on the object.

I need feedback from you! Thank you in advance!

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Reply #1 on: August 09, 2013, 10:01:24 pm »

the link http://hyperphysics.phy-astr.gsu.edu/hbase/frict3.html has good tips on friction

Friction Assumptions

In the standard model for friction between surfaces, there are certain inherent assumptions:

1. The frictional force is independent of area of contact   
2. The frictional force is independent of the velocity of motion   
3. The frictional force is proportional to the normal force.   

One can readily find circumstances where any or all of these assumptions are invalid, but they provide a straightforward framework for a beginning treatment of friction that satisfactorily describes many phenomena.

the applet can be include real life cases where the rule 1 is valid
and include real life case where rule 1 is not valid due to the increase in microscope contact area during broad tires on snow

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