Question

A man stands on a wooden plank of area of cross section 2500cm. he weighs 70kg and exerts a force of 500N. what is the pressure exerted by him on wooden plank??

Answer 1

$$\begin{gathered} \mathrm{Weight}\mathrm{of}\mathrm{the}\mathrm{man}=\mathrm{mass}\times \mathrm{g} \\ \mathrm{W}=\mathrm{mg} \\ \mathrm{W}\hspace{0.17em}=70\times 10(\mathrm{takin}\mathrm{g}=10\raisebox{1ex}{$\mathrm{m}$}\!\left/ \!\raisebox{-1ex}{${\mathrm{s}}^2$}\right.) \\ \mathrm{W}=700\mathrm{N} \\ \mathrm{force}\mathrm{exerted}\mathrm{by}\mathrm{the}\mathrm{man}\mathrm{on}\mathrm{the}\mathrm{planl}=\mathrm{F}=500\mathrm{N} \\ \mathrm{total}\mathrm{force}\mathrm{on}\mathrm{the}\mathrm{plank}=1200\mathrm{N} \\ \mathrm{Area}\mathrm{of}\mathrm{the}\mathrm{plank}=2500{\mathrm{cm}}^2=2500\times {10}^{-4}{\mathrm{m}}^2 \\ \mathrm{Pressure}\mathrm{on}\mathrm{the}\mathrm{plank}=\mathrm{P}=\frac{\mathrm{Total}\mathrm{Force}}{\mathrm{area}}=\frac{1200}{2500\times {10}^{-4}}=0.48\times {10}^4 \\ \mathrm{P}\hspace{0.17em}=4800\mathrm{Pa} \end{gathered}$$