# Maximum friction force before slipping occurs

1. Apr 11, 2009

### electricblue

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

Hi guys, i am sort of confused with the concept of slipping. I got a question.. what does it mean by maximum friction force before slipping occurs?

2. Relevant equations

I believe in the use of $$f_{}s$$ $$\leq$$ $$\mu_{}s$$n

3. The attempt at a solution

please correct me if i am wrong. maximum friction force before slipping occurs = $$\mu_{}s$$n

Last edited: Apr 11, 2009
2. Apr 11, 2009

### tiny-tim

Hi electricblue!

(have a mu: µ and a ≤ and try using the X2 tag just above the Reply box )
Yes, if the force needed was any more (than µsN), then the force available wouldn't be enough, and so there would be slipping.

3. Apr 11, 2009

### astrorob

Hi electricblue,

To make you understand this concept, consider a block placed on an angled slope.

The block can either;

1. Slide (the frictional force exerted on the slope by the contact surface of the object < the force component due to gravity acting on the block parallel to the slope).

2. Remain stationary (the frictional force exerted on the slope by the contact surface of the object >= the force component due to gravity acting on the block parallel to the slope).

Let's say that the block originally remains stationary.

Now let's increase the angle of the slope. This has the same effect as to increase the force component due to gravity acting on the block parallel to the slope (You may find this easier to conceptualise if you draw a diagram).

There will come a point when the block begins to slide, that is, when the maximum frictional force between the contact surface and the block is overcome. This maximum frictional force is given by the equation you've stated, in words:

Maximum frictional force = coefficient of friction x normal force

4. Apr 11, 2009

### electricblue

Ok thanks! I got it now

5. Apr 15, 2009

### electricblue

I have been studying this concept of slipping now it gets me pondered..

what if i have a crate on a truck and the truck is suppose to climb up a hill of 20 degrees. mass of crate is 100kg and coefficent of static friction and kinetic friction is 0.4 and 0.5 respectively. the question is: What is the maximum acceleration the truck can have without the crate slipping?

6. Apr 16, 2009

### astrorob

Hi again electricblue,

You're going to have to show some attempt before we can help you.

Hint: Use N2L and also work out the maximum frictional force before slipping.