Static friction: is it equal to μR or less than or equal to μR?

[Padford]

now on question 8 of my homework, and i am starting to wonder if i;ve been getting these question right. It's to do with friction.

Relativally simple question: When an object is stationary, would the formula to find the resolved friction be: F = (mew, u) R or F (is less-than-or-equal-to) (mew, u) R?!
sorry bout the notation, have NO idea how to use it!
thanks in advance
Padford.

 

[here]

friction

the normal force (force perpendicular to the plan of motion) is variable based on angle of incline or decline

 

[Padford]

thanks, but which formula applies to an object which is stationary, am i being stupid, co i swear our teacher told us one or the other?!

 

[here]

you have static and kinetic frction the difference is that the constants are different, think about sliding a large object its hard to get it sliding, but you get it sliding its not as hard,

 

[Doc Al]

Relativally simple question: When an object is stationary, would the formula to find the resolved friction be: F = (mew, u) R or F (is less-than-or-equal-to) (mew, u) R?!

Static friction is always less than or equal to $\mu N$, where N is the normal force pressing the surfaces together.

 

[Padford]

Thank you both very much! Very helpful

-Padford