I have a box at rest on a plane raised to the critical angle.(adsbygoogle = window.adsbygoogle || []).push({});

I need to derive the formula [tex]\mu_s=mgtan(\theta)[/tex]

I know [tex]f_s/n=\mu[/tex]

[tex]n=f_y=mgcos(\theta)[/tex]

[tex]f_s=f_x=mgsin(\theta)[/tex]

This leaves me with [tex]tan(\theta)=\mu[/tex] cause the mg cancel out.... what did I do wrong?

**Physics Forums | Science Articles, Homework Help, Discussion**

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Homework Help: How to derive coefficient of friction?

**Physics Forums | Science Articles, Homework Help, Discussion**