b
$\mathrm{f}_{\mathrm{K}}=\mu \mathrm{mg} \cos \theta$
$=0.1 \times \frac{50 \times \sqrt{3}}{2}$
$=2.5 \sqrt{3} \mathrm{~N}$
${F}_1=\mathrm{mg} \sin \theta+\mathrm{f}_{\mathrm{K}} $
$=25+2.5 \sqrt{3}$
$\mathrm{F}_2=\mathrm{mg} \sin \theta-\mathrm{f}_{\mathrm{K}}$
$\quad=25-2.5 \sqrt{3}$
$\therefore \mathrm{F}_1-\mathrm{F}_2=5 \sqrt{3} \mathrm{~N}$
