Homework Help: Coefficient of static friction on a ramp?

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1. Nov 16, 2015

katie beisel

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

2. Relevant equations
F = ma
fs = mus x FN

3. The attempt at a solution

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

2. Nov 16, 2015

Staff: Mentor

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.

3. Nov 16, 2015

katie beisel

i dont understand. using what equation?

4. Nov 16, 2015

Staff: Mentor

What equations would you apply if the mass were given?