Question 38469

May 30, 2017

The amount of surface area in contact with the ground is far less when the man is walking than when he is standing still.

Explanation:

If we calculate pressure as the the force exerted per unit area

color(white)(aaaaaaaaaaaaaa)"Pressure"= ("Force")/("Area")

and compare the pressure when walking (only the heel of 1 foot in contact, in this instance) vs. when standing still (both feet are in contact), taking the average weight of the man as $720 \text{ N}$, then

$\textcolor{w h i t e}{- -} {\text{Heel SA: 0.0064 m"^2 and "SA of both feet: 0.0258m}}^{2}$

$\textcolor{w h i t e}{a a}$

color(blue)"when walking"rArr"P"= ("720 N")/("0.0064 m"^2)=112500 N/m^2

$\textcolor{w h i t e}{- -} \text{vs}$

color(red)"when standing still"rArr"P"= ("720 N")/("0.0258 m"^2) = 27907 N/m^2#

we clearly see that the Pressure is $\text{4 x}$ greater when the person walks as opposed to when he stands still on both legs.