# The pressureWhat is the pressure at the bottom of Loch Ness, which is as much as 754 ft deep? (the surface of the lake is only 15.8m above sea level; hence, the pressure there can be taken to be...

The pressure

What is the pressure at the bottom of Loch Ness, which is as much as 754 ft deep? (the surface of the lake is only 15.8m above sea level; hence, the pressure there can be taken to be 1.013x10^5 Pa.)

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### 2 Answers

The pressure at the bottom of the lake is the weight of the water, minus the weight of the air (i.e. the air pressure at the lake surface), per unit area.

Water weighs 0.0361 pounds/ cubic inch

0.0361lbs/in^3*754ft*12 inches/ft = 326.6 lbs/in^2 (psi)

1 psi = 6895 Pa

326.6 psi = 6895*326.6 Pa = 22.52x10^5 Pa

22.52x10^5 Pa - 1.013x10^5 Pa = 21.5x10^5 Pa

754 ft = 754*30.48cm =229.8192meter depth.

The water column of 229.8192m has 229.8192*1000Kg*9.81 =2254526.352Pa pressure = 2.255*10^6 Pa

So the actual pressure at the bottom = water pressure+atmospheric pressure = 2.255*10^6+1.013*10^5

= (2.25545+0.1013)*10^6

=2.35675*10^6 Pa