Mentor

## why do trucks have bigger brakes?

Try this: a 1kg block is placed on a 45 degree inclined plane. The static friction coefficient is 0.5. Does it slide?

Mentor
 Quote by phyzzle In theory why can't the forces be equal to fs max? The forces would still be that of static friction as opposed to kinetic friction right?
That doesn't make sense from what we have been discussing. If the car is at rest then the force is 0 as you have correctly pointed out multiple times. It cannot be both 0 and the maximum.

In order for the force to be at f max you would have to be braking as hard as possible using ideal antilock brakes.

 Quote by DaleSpam That doesn't make sense from what we have been discussing. If the car is at rest then the force is 0 as you have correctly pointed out multiple times. It cannot be both 0 and the maximum. In order for the force to be at f max you would have to be braking as hard as possible using ideal antilock brakes.
I am not sure what we are talking about anymore. You asked:

"Why? There is only one equation that I know of which involves the coefficient of static friction and it allows for a range of forces for a constant coefficient. Are you aware of any formula other than fs≤μsfN which uses μs? If so, please post it with a reference."

and I responded with another formula, and it's reference. I do not think I ever implied that the static frictional force can be both 0 and the maximum, if I did I certainly did not intend to.
I came here with an honest question about something I did not understand, and thanks to your help and that of others I think I have clarity now. If your intention was to help my understanding you certainly did that, so...thank you.
 Mentor You are welcome. Sorry if my last comment caused any confusion. I was just answering that small question I quoted. The force can be f max under certain conditions, but not those discussed here.