# 11.4 Variation of pressure with depth in a fluid  (Page 3/4)

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## Conceptual questions

Atmospheric pressure exerts a large force (equal to the weight of the atmosphere above your body—about 10 tons) on the top of your body when you are lying on the beach sunbathing. Why are you able to get up?

Why does atmospheric pressure decrease more rapidly than linearly with altitude?

What are two reasons why mercury rather than water is used in barometers?

[link] shows how sandbags placed around a leak outside a river levee can effectively stop the flow of water under the levee. Explain how the small amount of water inside the column formed by the sandbags is able to balance the much larger body of water behind the levee.

Why is it difficult to swim under water in the Great Salt Lake?

Is there a net force on a dam due to atmospheric pressure? Explain your answer.

Does atmospheric pressure add to the gas pressure in a rigid tank? In a toy balloon? When, in general, does atmospheric pressure not affect the total pressure in a fluid?

You can break a strong wine bottle by pounding a cork into it with your fist, but the cork must press directly against the liquid filling the bottle—there can be no air between the cork and liquid. Explain why the bottle breaks, and why it will not if there is air between the cork and liquid.

## Problems&Exercises

What depth of mercury creates a pressure of 1.00 atm?

0.760 m

The greatest ocean depths on the Earth are found in the Marianas Trench near the Philippines. Calculate the pressure due to the ocean at the bottom of this trench, given its depth is 11.0 km and assuming the density of seawater is constant all the way down.

Verify that the SI unit of $\mathrm{h\rho g}$ is ${\text{N/m}}^{2}$ .

$\begin{array}{lll}{\left(h\rho g\right)}_{\text{units}}& =& \left(\text{m}\right)\left({\text{kg/m}}^{3}\right)\left({\text{m/s}}^{2}\right)=\left(\text{kg}\cdot {\text{m}}^{2}\right)/\left({\text{m}}^{3}\cdot {\text{s}}^{2}\right)\\ & =& \left(\text{kg}\cdot {\text{m/s}}^{2}\right)\left({\text{1/m}}^{2}\right)\\ & =& {\text{N/m}}^{2}\end{array}$

Water towers store water above the level of consumers for times of heavy use, eliminating the need for high-speed pumps. How high above a user must the water level be to create a gauge pressure of $3\text{.}\text{00}×{\text{10}}^{5}\phantom{\rule{0.25em}{0ex}}{\text{N/m}}^{2}$ ?

The aqueous humor in a person’s eye is exerting a force of 0.300 N on the $1\text{.}\text{10}{\text{-cm}}^{2}$ area of the cornea. (a) What pressure is this in mm Hg? (b) Is this value within the normal range for pressures in the eye?

(a) 20.5 mm Hg

(b) The range of pressures in the eye is 12–24 mm Hg, so the result in part (a) is within that range

How much force is exerted on one side of an 8.50 cm by 11.0 cm sheet of paper by the atmosphere? How can the paper withstand such a force?

What pressure is exerted on the bottom of a 0.500-m-wide by 0.900-m-long gas tank that can hold 50.0 kg of gasoline by the weight of the gasoline in it when it is full?

$1\text{.}\text{09}×{\text{10}}^{3}\phantom{\rule{0.25em}{0ex}}{\text{N/m}}^{2}$

Calculate the average pressure exerted on the palm of a shot-putter’s hand by the shot if the area of contact is $\text{50}\text{.}0\phantom{\rule{0.25em}{0ex}}{\text{cm}}^{2}$ and he exerts a force of 800 N on it. Express the pressure in ${\text{N/m}}^{2}$ and compare it with the $1\text{.}\text{00}×{\text{10}}^{6}\phantom{\rule{0.25em}{0ex}}\text{Pa}$ pressures sometimes encountered in the skeletal system.

The left side of the heart creates a pressure of 120 mm Hg by exerting a force directly on the blood over an effective area of $\text{15}\text{.}0\phantom{\rule{0.25em}{0ex}}{\text{cm}}^{2}.$ What force does it exert to accomplish this?

24.0 N

Show that the total force on a rectangular dam due to the water behind it increases with the square of the water depth. In particular, show that this force is given by $F=\rho {\mathrm{gh}}^{2}L/2$ , where $\rho$ is the density of water, $h$ is its depth at the dam, and $L$ is the length of the dam. You may assume the face of the dam is vertical. (Hint: Calculate the average pressure exerted and multiply this by the area in contact with the water. (See [link] .)

what's the period of velocity 4cm/s at displacement 10cm
What is physics
the branch of science concerned with the nature and properties of matter and energy. The subject matter of physics includes mechanics, heat, light and other radiation, sound, electricity, magnetism, and the structure of atoms.
Aluko
and the word of matter is anything that have mass and occupied space
Aluko
what is phyices
Whats the formula
1/v+1/u=1/f
Aluko
what aspect of black body spectrum forced plank to purpose quantization of energy level in its atoms and molicules
a man has created by who?
What type of experimental evidence indicates that light is a wave
double slit experiment
Eric
The S. L. Unit of sound energy is
what's the conversation like?
some sort of blatherring or mambo jambo you may say
I still don't understand what this group is all about oo
ENOBONG
no
uchenna
ufff....this associated with physics ..so u can ask questions related to all topics of physics..
what is sound?
Bella
what is upthrust
what is upthrust
Olisa
Up thrust is a force
Samuel
upthrust is a upward force that acts vertical in the ground surface.
Rodney
Paul
what is centre of gravity?
Paul
you think the human body could produce such Force
Anthony
what is wave
mirobiology
Angel
what is specific latent heat
the total amount of heat energy required to change the physical state of a unit mass of matter without a corresponding change in temperature.
fitzgerald
is there any difference between specific heat and heat capacity.....
what wave
Bryan
why medical physics even.we have a specoal branch of science biology for this.
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what is the s.i unit for work
joules
Aaron
Joules
EmmaTk