Question

a 240lb man is standing on both feet. the contact area for each shoe is 4 inches by 12 inches. the area of contact for each shoe is 48 inches. what is the pressure exerted on the floor.

Answer 1

here mass of man is 240 lb

here 1 lb = 0.453592 kg

so here for 240 lb = 240* 0.453592

= 108.862 kg

here we are find area of shoes = 12 * 4

= 48 inch ²

here area of shoes in inch² unit , so we have to change unit of area in to SI unit system unit = m²

here 1 inch² = 0.00064516 m²

here area , 48 inch² = 48 * 0.00064516

area , A = 0.0309677 m²

these the area of one shoes, here we have two shoes for two feet which are exerted pressure on floor,

so net total contact area , A_net = 2 * area of shoes

= 2 * A ( A = area of one shoes )

= 2 * 0.0309677

Anet = 0.0619354 m² ( A_net = total contact area of two shoes )

so here man stand on the floor, so here man extered some force on the floor due to gravity is equal to

F = mg

F= 108.862 * 9.8

F = 1066.8476 N

Here man exerted forced on the floor due to gravity = F = 1066.8476 N

here we wanto to find the pressure extered by man on the floor.

pressure is defined as " it is force per unit contact area "

so pressure , P = F / A

P = 1066.8476 /  0.0619354

P = 17225.1668674 N / m²  

P = 1.722 × 10⁴ N / m²

here pressure exerted by man on the floor is equal to   P = 1.722 × 10⁴ N / m²