9000038707

The box is on the slope as in the picture. The length of the slope is $l=2\mathrm{m}$ and the height is $h=1.2\mathrm{m}$. The forces acting on the box are the force of gravity $\overrightarrow{F_G}$ and the friction $\overrightarrow{F_t}$. The force of gravity can be replaced by two components $\overrightarrow{F_1}$ and $\overrightarrow{F_n}$. (The force $\overrightarrow{F_1}$ is parallel to the slope and $\overrightarrow{F_n}$ is perpendicular to the slope.) The friction $F_t$ is given by the formula $F_t=f{F}_n$ where $f$ is the coefficient of the friction. Consider the standard acceleration of gravity $g=10\mathrm{m}{\mathrm{s}}^{-2}$. Find the minimal value for the coefficient of the friction $f$ to ensure that the box does not move with an acceleration.