Coefficient of static friction on a ramp?

[katie beisel]

Homework Statement

A small block sits at the midpoint of a 2.0 m plank lying on a level floor. A student slowly raises one end of the plank until the block starts to slide. At that instant, the raised end is 0.55 m above the floor. Find the coefficient of static friction between block and plank.

Homework Equations

F = ma
fs = mus x FN

The Attempt at a Solution

so i turned it into a triangle and the sides are 1.9, .55, 2.0
there's no mass given so I'm not sure how to even begin to find the force of friction or force normal

 

[gneill]

Work symbolically. Leave the mass as an unknown "m" and work through the algebra. You should find that the m will cancel out along the way.

 

[katie beisel]

Work symbolically. Leave the mass as an unknown "m" and work through the algebra. You should find that the m will cancel out along the way.

i don't understand. using what equation?

 

[gneill]

i don't understand. using what equation?

What equations would you apply if the mass were given?