the “internal” or “thermal energy”of moving molecules is already something we have...

The “internal” or “thermal energy”of moving molecules is already

something we have identified with

TEMPERATURE

LIQUIFIES/BOILS SOLIDIFIES/MELTS

MERCURY 356.58oC -38.87oC

WATER 100.00oC 0.000oC

NITROGEN -195.8oC -210.1oCOXYGEN -183.0oC -218.4oCHYDROGEN -252.5oC -259.1oCHELIUM -268.6oC -272.1oC

Pre

ssur

e (l

b/in

2 )0oC 100o-100o-200o

20

15

10

5

roomtemperature

Pre

ssur

e (l

b/in

2 )0oC 100o-100o-200o-300o

20

15

10

5

Absolute zero-273.15oC

Pre

ssur

e (l

b/in

2 )

273.15 373.150 K

20

15

10

5P T

Provided T is measure in the Kelvin scale

A head-on collision between identicalmolecules just exchanges momenta:

v1 v2

v1v2

Glancing blows are a little more complicated.

But you may remember the normal components of motion

just exchange as in head-on collisions

While the perpendicular components(parallel to the contact surface between them)

remain unaffected.

The total momentum and kinetic energyremains unchanged in such collisions.

And there is stillthe same amount ofmomentum being

carriedupward/downward

and left/right.

The more and more and more air we forceinto a tire (basketball or football) the more taut its rubber/fabric casing becomes andthe firmer and more solid its surface grows.

Pressure number of moleculestrapped in a container

We also saw by a simple demonstrationthat this pressure is

UP as well as DOWN

and

increased as the speed of the particles creating it increased.

mv

-mv

Impulse delivered to wall

2mv

The force of any individual impact in a collision is

delivered by the impulse

mvF ∝mvtF Δ=Δ

In any interval of time, the number of times a single particle will return to

strike the wall again and again v

mvF ∝Impact of any single collision:v∝Rate of collisions:

Pressure mv2Together, both imply

Pressure number of moleculestrapped in a container

All together:

Pressure number of molecules

kinetic energy of the molecules

Not forgetting:

Which is what Temperature really measures!

Raising Tincreases

molecular kinetic energy

outward pressure of gas

volume occupied by gas

Some of the expanding air escapes out the bottom; it takes less of the warmer air to fill

the same space as the cooler air.

Essentially the SAME VOLUMEnow occupied by less gas

…which weighs less!

P1 P2

Static equilibrium of fluids

• All fluids have settled.

• Pressures have equalized and are exerted in all directions.

• No fluid is moving.P1 = P2

Only when there’s a pressure difference

P1 P2

can there be any acceleration

with flow from regions of high pressure to regions of lower pressure.

The Diaphragm(during inhalation)

Increasing the VOLUME of the lungsreduces the pressure of the gas inside.

External air at ~1 atmosphere of pressure is forced in!

Simple Ball Float Valve prevents drains from backing up

Ordinarily water drains easily,

but a backed up sewer during astorm seals thefloating ball sono water flows into your home.

Any water above the draincannot push down the ballfloat unless its standing water with pressure greater thanthat pushing the ball float up.

Float valve!

Raising the sealed pistoncreates a vacuum beneathit. Assuming at least Atmospheric pressure is exerted on the reservoir of water beneath, water will be pushed up this pipe.

Similar to the manualbicycle tire pump:

Float valve!

Raising the sealed pistoncreates a vacuum beneathit. Assuming at least Atmospheric pressure is exerted on the reservoir of water beneath, water will be pushed up this pipe.

Similar to the manualbicycle tire pump:

Another “Positive Displacement” Pump

Much simpler to understand is the impeller pump

which can continuouslydrive water through.

OUT

IN

Momentum Transfer Pumps

Industrial impeller