Because we grew up in a pressurized systern, our bodies have developed so that a

Question

Because we grew up in a pressurized systern, our bodies have developed so that all pressures interior to our body are relatively close to atmospheric pressure. With small pressure differentials, we have a difficult time gauging the magnitude of atmospheric pressure. Consider a person lying on his stomach, with sheets of paper stacked on his back. If each sheet of paper has a mass of 2.800 g and is the standard letter size (8.5"x 11"), how many sheets would stack to produce a pressure on his back equal to atmospheric pressure (roughly 101325 Pa)? Number

Explanation / Answer

2.800g = 0.0028 kg

8.5 inch = 0.216 m

11 inch = 0.279 m

The weight of N sheets is N*mg, with m the mass of one sheet and g the acceleration due to gravity.
The pressure equals weight divided by the area on which the weight presses:

p= F/A = Nmg/(L*W)

Therefore

N = p*L*W / (m g)

= 101325 N/m^2 * 0.279m*0.216m / (0.00280 kg * 9.81N/kg)
= 222304

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