In the figure shown a force $\overrightarrow{F}=(\widehat{\mathrm{i}}+4\widehat{\mathrm{j}}) N$ acts on a 1 kg block. ,what is the force of friction acting on the block ?

$\begin{array}{l}\overrightarrow{F}=\left(\hat{i}+4\hat{j} \right)\stackrel{\backslash }{N \mathrm{and}} \mathrm{m}=1\mathrm{kg}\\ \mathrm{mg}=10 N.\\ \mathrm{If} \mathrm{N} \mathrm{be} \mathrm{the} \mathrm{normal} \mathrm{reaction} ,\\ \mathrm{then} \mathrm{N}+4=\mathrm{mg}\\ \mathrm{N}+4=10\\ \mathrm{N}=6 N\\ f_{max}=\mathrm{\mu N}\\ =0.3\times 6 N=1.8\mathrm{N}\end{array}$

Force in horizontal direction is 1 N which is less than 1.8 N then force of frictions is $-\widehat{i}$