Physics - W.E.P. Question with Solution | TestHub

Initial K.E., $E_1=\frac{1}{2}m{v}^2$ $$=\frac{1}{2}\times 10\times (10{)}^2=500\mathrm{J}$$ At $x=20\mathrm{m}$, retarding force, $$F_1=0.1\times 20=2\mathrm{N}$$ At $x=30\mathrm{m}$, retarding force, $$F_2=0.1\times 30=3\mathrm{N}\text{. }$$ Average Retarding Force $F=\frac{F_1+F_2}{2}=\frac{2+3}{2}=2.5$ Work done by retarding force $=$ loss in K.E. $$=F\times s=2.5(30-20)=25\mathrm{J}$$ Final K.E. $=E_1-\mathrm{loss}$ in K.E. $=500-25=475\mathrm{J}$