Forces & Friction: Which is Greater?

AI Thread Summary
The discussion centers on comparing the force required to lift a box versus the force needed to pull it along a surface, with the consensus leaning towards lifting requiring more force. The coefficient of friction, which influences the pulling force, typically ranges between 0 and 1, but some participants mention instances where it can exceed 1, particularly in unusual materials. References to coefficients greater than 1 are noted, such as aluminum on aluminum and lead on steel, though these cases are rare. The conversation highlights the complexity of frictional forces and their dependence on material properties. Understanding these dynamics is crucial for accurately assessing forces in physics problems.
lola2000
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Homework Statement


A student measures the the force required topull a box along the floor and then the force required to lift the box onto a table. Which is greater?

Homework Equations

The Attempt at a Solution


[/B]
Is it the force to lift the box since frictional force is the normal force or weight times the coefficient of friction which is between 0 and 1?
 
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lola2000 said:

Homework Statement


A student measures the the force required topull a box along the floor and then the force required to lift the box onto a table. Which is greater?

Homework Equations

The Attempt at a Solution


[/B]
Is it the force to lift the box since frictional force is the normal force or weight times the coefficient of friction which is between 0 and 1?
The coefficient of friction can be greater than 1.
 
SammyS said:
The coefficient of friction can be greater than 1.
Is there a reference saying that the coefficient of kinetic friction can be greater than 1?

Chet
 
Chestermiller said:
Is there a reference saying that the coefficient of kinetic friction can be greater than 1?

Chet
It is highly unusual even for static friction.

I have seen a few values listed with μk > 1 .

Al on Al showed 1.3 & 1.4 in a couple of tables.

Lead on steel in one or two tables -- I don't recall the value.

I don't why intrinsically that it's not possible for μk > 1 , but I don't have any good references.
 
SammyS said:
It is highly unusual even for static friction.

I have seen a few values listed with μk > 1 .

Al on Al showed 1.3 & 1.4 in a couple of tables.

Lead on steel in one or two tables -- I don't recall the value.

I don't why intrinsically that it's not possible for μk > 1 , but I don't have any good references.
Thanks. Very interesting. I'll file this away in my brain.

Chet
 

Thread 'Errors and significant figures'

I multiplied the values first without the error limit. Got 19.38. rounded it off to 2 significant figures since the given data has 2 significant figures. So = 19. For error I used the above formula. It comes out about 1.48. Now my question is. Should I write the answer as 19±1.5 (rounding 1.48 to 2 significant figures) OR should I write it as 19±1. So in short, should the error have same number of significant figures as the mean value or should it have the same number of decimal places as...
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Thread 'A cylinder connected to a hanging mass'

Thread 'A cylinder connected to a hanging mass'

Let's declare that for the cylinder, mass = M = 10 kg Radius = R = 4 m For the wall and the floor, Friction coeff = ##\mu## = 0.5 For the hanging mass, mass = m = 11 kg First, we divide the force according to their respective plane (x and y thing, correct me if I'm wrong) and according to which, cylinder or the hanging mass, they're working on. Force on the hanging mass $$mg - T = ma$$ Force(Cylinder) on y $$N_f + f_w - Mg = 0$$ Force(Cylinder) on x $$T + f_f - N_w = Ma$$ There's also...
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