- #1

leroyjenkens

- 616

- 49

## Homework Statement

Here's a picture of the set up.

I need to find out what angle I need to have the plane raised to so that the blocks aren't moving.

## Homework Equations

F = ma

## The Attempt at a Solution

For the first block

[tex]F_k=μ_kF_N[/tex]

[tex]F_T+F_N-μ_kF_N+2mgcosθ+2mgsinθ=0[/tex]

Since the [tex]F_N[/tex] and [tex]2mgcosθ[/tex] cancel each other, I eliminated them from the problem. I set the right side equal to 0 since there is no acceleration

Then I get

[tex]F_T = μ_kF_N + 2mgsinθ[/tex]

For the right block [tex]mg = F_T[/tex]

So I input that into my equation for the other block and get

[tex]mg=μ_kF_N+2mgsinθ[/tex]

For [tex]F_N[/tex] I plug in [tex]2mgcosθ[/tex]

And get [tex]mg=μ_k2mgcosθ+2mgsinθ[/tex]

And this is when I know something is wrong. That [tex]μ_k[/tex] is the coefficient for kinetic friction, not static friction, and I have [tex]sinθ[/tex] and [tex]cosθ[/tex], so that's two unknowns.

How do I find out the coefficient for static friction? Do I even need it?

And what went wrong with my analysis of this problem?

Thanks.