2
$\begingroup$

Is there a material that has higher kinetic friction than static friction?

You can assume it's sliding on any surface you want.

Better if you come up with one that has this property on a standard flooring material: steel, wood, smooth concrete, tile, asphalt, etc.

Also better if the material has this property at a macro scale.

Improve this question
$\endgroup$
3
  • 1
    $\begingroup$ Does shear thickening material count? $\endgroup$
    – hazzey ♦
    May 4 '16 at 1:20
  • $\begingroup$ You might consider specifying if you are interested in viscous friction (fluids) or Coulomb (sliding) friction. $\endgroup$
    – willpower2727
    May 4 '16 at 13:29
  • $\begingroup$ I don't think it exists, but it could be that a material rapidly heats up upon moving, increasing the friction by that. Mostly friction reduces under temperature, but some materials don't, like hazzey mentioned. $\endgroup$
    – Bart
    May 7 '18 at 15:27
4
$\begingroup$

Friction is not a property of a material, it is a property of the interface between two objects, which may be the same or different materials. One interface I can think of that has that property is a thin layer of grease -- the force required to move increases with velocity.

Improve this answer
$\endgroup$
1
  • $\begingroup$ But that force is not "caused" by kinetic friction, so it does not really answer the question. $\endgroup$
    – fibonatic
    May 5 '16 at 21:49
2
$\begingroup$

Sliding friction must, logically always be less than static friction. This becomes obvious when you look at it in terms of forces rather than coefficients.

Consider a block resting on a flat surface. You apply a small force to one side of the block to try to slide it along. Initially it doesn't move as the reaction force provided by friction increases in line with the force you exert.

Say that applying 10N of force is just enough to overcome static friction and get the block moving. Now if the sliding friction becomes greater the 10N force is no longer enough to overcome it and so it stops and your back to a static condition.

Another way to look at this is that friction is a reaction force so it can never be greater than the force applied otherwise you would be effectively getting work from nowhere.

However it is certainly possible to have materials whose friction properties change as a result of friction, for example carbon-carbon brakes are most effective at quite high temperatures.

There is also viscous drag which is proportional some function of speed although it is not really very meaningful to talk about static friction in this context.

Improve this answer
$\endgroup$
1
$\begingroup$

Apparently Aluminium - Aluminium (clean and dry) has a higher coefficient for kinetic friction than static friction.

The numbers I've found listed are:

  • Static: 1.05-1.35
  • Kinetic: 1.4

source source

Improve this answer
$\endgroup$
0
$\begingroup$

I dont think so. as kinetic force is always lesser than static. Here is a similar discussion

Similar question

The link is about the theory behind the static and kinetic friction. the coefficient of static friction can never be less than the coefficient of kinetic friction. Having greater kinetic than static friction just doesn't make any sense.

Improve this answer
$\endgroup$
4
  • $\begingroup$ This reads as a comment and not a full answer. Linking to an external site, even a StackExchange site, without an explanation or summary of the linked site is a poor answer. Explain why another reader may want to click through. Summarize the findings from the other question. $\endgroup$
    – user16
    May 4 '16 at 12:06
  • $\begingroup$ My bad. I dont think so. as kinetic force is always lesser than static. Here is a similar discussion [Similar question][1] [1]: physics.stackexchange.com/questions/541/… So, the link is about the theory behind the static and kinetic friction. the coefficient of static friction can never be less than the coefficient of kinetic friction. Having greater kinetic than static friction just doesn't make any sense. $\endgroup$
    – albseb
    May 4 '16 at 13:34
  • 1
    $\begingroup$ @albseb Please edit that into your answer instead of posting it as a comment. $\endgroup$
    – hazzey ♦
    May 4 '16 at 13:41
  • $\begingroup$ yea, it was not allowing me to edit earlier. $\endgroup$
    – albseb
    May 4 '16 at 14:22

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.