The “internal” or “thermal energy”of moving molecules is already something we have identified with TEMPERATURE LIQUIFIES/BOILS SOLIDIFIES/MELTS MERCURY o C o C WATER o C o C NITROGEN o C o C OXYGEN o C o C HYDROGEN o C o C HELIUM o C o C

Pressure (lb/in 2 ) 0oC0oC 100 o -100 o -200 o room temperature

Pressure (lb/in 2 ) 0oC0oC 100 o -100 o -200 o -300 o Absolute zero o C Pressure (lb/in 2 ) K P  TP  T Provided T is measure in the Kelvin scale

A head-on collision between identical molecules just exchanges momenta: v1v1 v2v2 v1v1 v2v2

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 energy remains unchanged in such collisions. And there is still the same amount of momentum being carried upward/downward and left/right.

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

Pressure  number of molecules trapped in a container We also saw by a simple demonstration that 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

In any interval of time, the number of times a single particle will return to strike the wall again and again  v Impact of any single collision: Rate of collisions: Pressure  mv 2 Together, both imply

Pressure  number of molecules trapped in a container All together: Pressure   number of molecules kinetic energy of the molecules Not forgetting: Which is what Temperature really measures!

Raising T increases 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 VOLUME now occupied by less gas …which weighs less!

P1P1 P2P2 Static equilibrium of fluids All fluids have settled. Pressures have equalized and are exerted in all directions. No fluid is moving. P 1 = P 2 Only when there’s a pressure difference P 1  P 2 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 lungs reduces 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 a storm seals the floating ball so no water flows into your home. Any water above the drain cannot push down the ball float unless its standing water with pressure greater than that pushing the ball float up.

Float valve! Raising the sealed piston creates a vacuum beneath it. Assuming at least Atmospheric pressure is exerted on the reservoir of water beneath, water will be pushed up this pipe. Similar to the manual bicycle tire pump:

Float valve! Raising the sealed piston creates a vacuum beneath it. Assuming at least Atmospheric pressure is exerted on the reservoir of water beneath, water will be pushed up this pipe. Similar to the manual bicycle tire pump:

Another “Positive Displacement” Pump

Much simpler to understand is the impeller pump which can continuously drive water through. OUT IN Momentum Transfer Pumps

Industrial impeller