Monday, October 20, 2014

1–47E

1–47E A 200-pound man has a total foot imprint area of 72
in2. Determine the pressure this man exerts on the ground if
(a) he stands on both feet and (b) he stands on one foot.
ANS
1-47E The weight and the foot imprintarea of a person are given. The pressures thisman exertson the ground when he stands on one and on both feetare tobe determined. Assumptions The weightof the person isdistributed uniformlyon footimprintarea. Analysis The weightof the man isgiven tobe 200 lbf. Noting thatpressure is force per unitarea, the pressure thisman exertson the ground is (a) On both feet: psi 2.78 = = × = = lbf/in 78 . 2 in 36 2 lbf 200 2 2 2 A W P (b) On one foot: psi 5.56 = = = = lbf/in 56 . 5 in 36 lbf 200 2 2 A W P Discussion Notethatthe pressure exerted on the ground (and on the feet) isreduced by halfwhen the person stands on both feet.

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