Solution 3.9b
From Mechanics
Friction will "try" and prevent motion that is achieve equilibrium.
\displaystyle \begin{align}
& \text{For}\ \text{equilibrium}\ P-F=0 \\
& \text{that}\ \text{is}\ F=760\ \text{N} \\
\end{align}
Also the maximum friction possible is
\displaystyle \mu R=0.4\times 1960=784\ \text{N}.
\displaystyle F=760\ \text{N}
falls inside this maximum value and thus is the value of the friction.
