The resistance a surface or object encounters when moving over another.
Questions tagged [friction]
2717 questions
23
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3 answers
Why do people recommend wider tyres in car for better road grip?
Tyre companies boast of their wider tires for better grip on road. Also, the F1 cars have broad tires for better grip. But as far as I know Friction does not depend on the surface area of contact between the materials. Even the formula says so..…
Saurabh R S
- 406
17
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3 answers
Does the force of kinetic friction increase with the relative speed of the objects involved? If not, why not?
Does the force of kinetic friction increase with the relative speed of the objects involved?
I have heard and read that the answer is no. This is counter intuitive, and is a big part of why the "Airplane on a Treadmill" question is so…
John Gietzen
- 313
11
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4 answers
Does the contact area affect friction forces?
I recall studying a law of friction some years ago, in engineering school. All I remember is that when first approximation was taken, the popular $f=k \times N$ was derived.
Why would such an approximation be deemed so useful as to be taught as…
Vorac
- 680
11
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2 answers
If friction is caused by the reaction of molecules between the two surfaces, why doesn't a force act when you lift the object?
You have to break the bonds either way, be it lifting the object or moving it. Why is it that we don’t have to overcome the force required to break the cluster of molecules?
A J
- 125
10
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2 answers
Grip of the train wheels
How do the wheels of a train have sufficient grip on a metal track? I mean both of the surfaces are smooth (and not flexible) and it is okay if there is no inclination, but how about on an inclined track?
sterz
- 303
10
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3 answers
why making a surface "super" smooth increases the coefficient of friction?
I read that:
If you take a rough surface and make it smooth, the coefficient of friction decreases. But if you make it super smooth, then the coefficient of friction increases. How come?
claws
- 7,255
7
votes
4 answers
Why does a rotating tire use the static, rather than the dynamic coefficient of friction?
The explanation I have heard of the difference between static and dynamic friction is that static friction is stronger because bonds form when one object is put on top of another object and these have to be overcome to get the movement started.
For…
Casebash
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On a bicycle, why does my back tyre wear so much more quickly than the front?
This question is cross-posted from Bicycles.SE, but it is really one for those that know a bit about physics.
Why does the back tyre of a bicycle wear out quicker than the front tyre?
I have my uneducated suspicions but I would appreciate an…
ʍǝɥʇɐɯ
- 249
6
votes
2 answers
Does kinetic friction increase as speed increases?
Possible Duplicate:
Does the force of kinetic friction increase with the relative speed of the objects involved? If not, why not?
Layman alert...I last did physics in high school, and am just trying to understand something my son is working on.…
Paul Harvey
- 63
6
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3 answers
Model of contact friction
Consider the standard model of kinetic contact friction taught in introductory physics courses: $$F_f=\mu_k*F_N$$
According to this model, for a block with initial speed $v$ moving on a horizontal surface the speed as a function of time is…
math_lover
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Would a three wheeled vehicle be faster than a four wheeled vehicle of the same weight?
If I have a four wheeled vehicle (small wooden block with metal nail axles and plastic wheels) and apply a force X to it, would it be made faster by keeping one wheel off the ground in order to reduce friction? My thought is that the remaining…
Ethereal
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Why does a tire produce more traction when sliding slightly?
It is well known in racing that driving the car on the ideal "slip angle" of the tire where it is crabbing slightly from the pointed direction produces more cornering speed than a lower slip angle or a higher one.
(More explanation as requested)…
james creasy
- 235
4
votes
4 answers
Direction of frictional forces on front and back wheels
Why are the directions of frictional forces on the front and rear wheels of a moving car in the opposite direction, when the only the front wheels are accelerated (or only the back wheels)?
When the car accelerates, the direction of the static…
4
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2 answers
Force applied perpendicular to direction of motion, static or kinetic friction?
Let's assume we have a 1 kg cube on a flat uniform surface. The coefficients of friction between them are $\mu_k = 0.25$ and $\mu_s = 0.50$. This cube is moving at 1 m/s in the y direction, with whatever force is needed to overcome friction being…
DaleSwanson
- 145
4
votes
3 answers
Twisting a tightly fitting rod
Consider the task of extracting a cylindrical rod held by friction in a tightly fitting shaft. Instinctively one would tend to twist the rod around its axis while pulling. The question is, what is the physical basis for this? Does applying a torque…
user60437
- 86