Question: A block of mass $m$ is placed on an inclined plane with angle of inclination $\theta$. Let $N$, $f_L$ and $F$ respectively represent the normal reaction, limiting force of friction and the net force down the inclined plane. Let $\mu$ be the coefficient of friction. The dependence of $N$,$f_L$ and $F$ on $\theta$ is indicated by plotting graphs as shown below. Then curves (1), (2) and (3) respectively represent _____ respectively.
Answer:$F$,$N$ and $f_L$
I need an explanaton