Chapter 5, Problem 9PE

Show that the acceleration of any object down an incline where friction behaves simply (that is, where $f_{\text{k}}={\mu }_{\text{k}}N$ ) is $a=g\left(\sin \theta -{\mu }_{\text{k}}\cos \theta \right)$. Note that the acceleration is independent of mass and reduces to the expression found in the previous problem when friction becomes negligibly small $\left({\mu }_{\text{k}}=0\right)$.