Chapter 20, Problem 26A

We can understand how pressure in water depends on depth by considering a stack of bricks. The pressure below the bottom brick is determined by the weight of the entire stack. Halfway up the stack, the pressure is half as great as it is at the bottom because the weight of the bricks above is half as great. To explain atmospheric pressure, we should consider compressible bricks, like foam rubber. Why is this so?

To determine

To Explain: The atmospheric pressure.

Explanation of Solution

Introduction:

Atmospheric pressure is also called barometric pressure and is defined as the pressure due to the air column. The standard atmosphere is the unit of pressure and can be defined as

  $1\text{ atm = 101,325 Pa}$ which is equal to $760\text{ mm Hg}$ .

The air compresses under pressure, unlike the bricks. This increase in pressure also increases the density of air at the bottom. This difference in density causes more of the atmospheric mass towards the ground than towards outer space. If the bricks were replaced by air or compressed under the pressure, the density at various height would better model that of the atmosphere.