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Problem# h2phy1 - Pressure inside the Aorta

Problem# h2phy2 - Pressure on the floor

A living room has floor dimension of 3.5 m and 4.2 m and height of 2.4 m.
a. What does the air in the room weight?
b. What force does the atmosphere exert on the floor of the room?

Strategy - the rule "Must have" of Mr.Zhang ® material for solving this problem ; (1) w=mg    (2) m=ρv    (3) ρ=F⊥/A

Material or Object         Density (kg/m3)     Air: 20 οC and 1 atm 1.21

Solution a) The air in the room weighs;  w=mg    →(1)  m=ρv    →(2) We take (2) substitue in (1) ∴  W=ρairvg ∴  W = (1.21 kg/m3)(3.5 m x 4.2 m x 2.4 m)(9.8 m/s2 ∴  W = 418 kg m/s2 ∴  W = 418 N

Ans.   ∴The air in the room weighs 418 N

b) What force does the atmosphere exert on the floor of the room?  ρ=F⊥/A  ρatm=F⊥/A  F⊥=ρatmA  F⊥=1.01x105 N/m2)(3.5 m x4.2 m)  F⊥=1.5x106 N

Ans.   ∴The atmosphere exerts 1.5x106 N on the floor of the floor Brake Booster