Physics

Project

Subject:

Pressure

By:

Cem Salur

Grade:

10/A

To:

Mr. Sinan Kosak

Content



What is Pressure?



Density



Pressure in liquids



What is Atmospheric Pressure?



Barometer



Manometer



Test 1



Test 2



Test 3



Test 4

What is pressure?

The word pressure has an exact meaning.

It is defined as the force acting normally

(perpendicularly) per unit area. Pressure

measured as Pascal “Pa”.

Pressure

=

Force

Area

N

m
2

Pa

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e

Question

A boy of mass 40 kg balances
evenly on two stilts, each an area
of 8 m

2

in contact with the ground.

What is the pressure exerted on
one stilt?

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Answer

Pressure= Force / area
Force= 400 N

Pressure=?

Area= 8 m

2

So
Pressure= 400 N / 8 m

2

Pressure= 50 Pa

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Density

Density is the mass per unit
volume of the substance, and it is
sometimes given the symbol “ρ”.

ρ = m / v ρ is density (kg/m3)
m is mass (kg)

v is volume (m3)

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Pressure in liquids

The pressure in liquid

increases with depth. The

width or shape of the

container doesn’t effect

the pressure. The pressure

is effected by the density

of the liquid. As the figure

show on the right side. In

liquids pressure acts all

directions not only

vertically.

The main formula is:

Pressure=force (weight) /

Area



hAdg / A



Which becomes => hdg

so

Pressure= hdg

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What is Atmospheric

Pressure?

On the earth we are living under a

large volume of air. Air has weight

and as a result the atmosphere

exerts a pressure not only on the

Earth’s surface but on objects on

the earth. Atmospheric pressure

is normally expressed in Newton's

per meter square or pascals (Pa).

The average value is 100 000 Pa

approximately. It gets less as one

goes up through the Earth’s

atmosphere until it becomes

virtually zero at a height of about 8

km.

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Barometer

There are two types of barometers:



Mercury Barometer



Aneroid Barometer

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Mercury Barometer

This is a long glass tube,

sealed at one end, with
the other end dipped in
a dish of liquid mercury.
Atmospheric pressure
sometimes measured in
millimeters of mercury
rather than pascal.
Mercury is used in a
barometer rather than
any other liquid,
because it is so dense.

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Aneroid Barometer

This is the barometer which

people hang in the hall to
forecast the weather. It isn’t
so accurate as mercury
barometer. But it is simpler
to read and to carry. In the
middle of barometer is
sealed metal box with
flexible sides. Most of the air
has been removed from the
box, so it is squashed by
the atmosphere. The greater
the pressure, the more the
sides are pushed in, and the
further the pointer moves
round.

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Manometer

Manometers are

used to measure
gas and liquid
pressure. The
height difference
tells you the extra
pressure.

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Test I

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Test II

Test III

Test IV