A body starts from rest on a long inclined plane of slope 45°. The coefficient of friction between the body and the plane varies as μ=0.3 x, where x…

A body starts from rest on a long inclined plane of slope $\displaystyle 45$°. The coefficient of friction between the body and the plane varies as $\displaystyle \mu=0.3 x$, where $\displaystyle x$ is distance travelled down the plane. The body will have maximum speed (for $\displaystyle \mathrm{g}=10 \mathrm{~m} / \mathrm{s}^2$ ) when $\displaystyle x=$ :