# Homework Help: Forces and friction

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1. Apr 16, 2015

### lola2000

1. The problem statement, all variables and given/known data
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?

2. Relevant equations

3. The attempt at a solution

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?

2. Apr 16, 2015

### SammyS

Staff Emeritus
The coefficient of friction can be greater than 1.

3. Apr 16, 2015

### Staff: Mentor

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

Chet

4. Apr 16, 2015

### SammyS

Staff Emeritus
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.

5. Apr 16, 2015

### Staff: Mentor

Thanks. Very interesting. I'll file this away in my brain.

Chet