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Can the coefficient of friction ever be greater than 1?

I'm just curious, as, although it has usually been maintained in A-level mechanics that

\mu \leq 1

, it seems intuitive that some materials would require a greater applied horizontal force than the normal reaction force to induce movement. So, can

\mu > 1

ever be true?

Reply 1

calcium878

18

Yes, though quite rarely in maths questions.

Reply 2

DoMakeSayThink

15

Yes. Why, when wearing shoes, do we find it easier to walk than drag our shoes along the ground?

Reply 3

musti123

11

No its between 0 and 1, think about it tis always easaier to drag something heavy than lisft in, try lifting ur desk, then try pushing it

Reply 4

Quoz

DoMakeSayThink

Yes. Why, when wearing shoes, do we find it easier to walk than drag our shoes along the ground?

Stupid example. Internal/External forces.

Reply 5

bballer4life

13

it can be more than 1.
i've done M3, and i remember my teacher telling me it can be greater than 1

Reply 6

RyanT

15

musti123

No its between 0 and 1, think about it tis always easaier to drag something heavy than lisft in, try lifting ur desk, then try pushing it

What about a superfluid thats very heavy? sweet all friction but gravity gives it some weight.

Reply 7

Lapis lazuli

2

It can be. Wikipedia gives an example of a tyre being greater than 1.

Reply 8

shamrock92

15

Yeah, it can be. Walter Lewin's stuff on friction on YouTube explains it all nicely

Reply 9

shunter7634

9

musti123

No its between 0 and 1, think about it tis always easaier to drag something heavy than lisft in, try lifting ur desk, then try pushing it

Yes it can - this table gives some nice examples.
http://www.engineeringtoolbox.com/friction-coefficients-d_778.html

Reply 10

DoMakeSayThink

15

Quoz

Stupid example. Internal/External forces.

Put a shoe (with some tread) on the pavement, and it's going to be easier to lift it than push it along. The example I gave is simply so people can relate. Anyway, care to elaborate on 'internal/external forces'?

Reply 11

benwellsday

12

I guess I'm wrong but I figured at the time it was because the coeffecient of friction had to be a ratio to make sure energy is conserved. I guess in general F = uR so if u > 1 then the frictional force is greater than the normal reaction force, which seems pretty possible really. And I guess conservation of energy isn't really related. I probably wasn't as interested back in M1 or M2 when it was introduced.

Reply 12

Hashshashin

13

Yep.

It´s nowhere near as cool, however, as having a coefficient of restitution which is greater than one.

From Wikipedia:
"A COR greater than one is theoretically possible, representing a collision that generates kinetic energy, such as land mines being thrown together and exploding."

:p:

Reply 13

qgujxj39

OP

17

Hashshashin

Yep.

It´s nowhere near as cool, however, as having a coefficient of restitution which is greater than one.

From Wikipedia:
"A COR greater than one is theoretically possible, representing a collision that generates kinetic energy, such as land mines being thrown together and exploding."

:p:

Now that is cool :yep:

Reply 14

Lithium

13

bballer4life

it can be more than 1.
i've done M3, and i remember my teacher telling me it can be greater than 1

I'll second on that, the F.Co can be >1, but not usually used...as far as i remember... :yep:

Reply 15

Simba

16

Hashshashin

Yep.

It´s nowhere near as cool, however, as having a coefficient of restitution which is greater than one.

From Wikipedia:
"A COR greater than one is theoretically possible, representing a collision that generates kinetic energy, such as land mines being thrown together and exploding."

:p:

Now I have a reason to go back to my college to poke my maths teacher for saying it was always < 1 :wink:

...

Reply 16

Vjyrik

10

Hashshashin

Yep.

It´s nowhere near as cool, however, as having a coefficient of restitution which is greater than one.

From Wikipedia:
"A COR greater than one is theoretically possible, representing a collision that generates kinetic energy, such as land mines being thrown together and exploding."

:p:

mmm

Reply 17

Hashshashin

13

Vjyrik

I hope you know the difference between Coefficient of Restitution and Coefficient of Friction.

Did you even read my post properly??

Reply 18

Vjyrik

10

Hashshashin

Did you even read my post properly??

Nope

Reply 19

Life Saver

1

Lol that's a silly question...In general the coefficient of friction is less than one. For a heavily polished surface the frictional force increases due to the increase of inter atomic forces. In such a case coefficient of friction will be greater than one.Next time when you are asking a question just think about it once . I have already wasted 1:45 sec typing this already. See ya

Can the coefficient of friction ever be greater than 1?

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