Too good to be true?

[TimberWolf]

Oh no we're not.

The pressure required to keep our feet off the ground would be quite unbearable not to mention messy.

Air pressure acts over our entire surface area (100,000 Newtons per metre squared, or around 10 thousand tonnes in weight per metre squared, but this pressure decreases with height, hence we are subjected to a small buoyant force. This is not enough for us to float in air.

It's the electromagnetic force that's keeps us from becoming part of the ground.

True.

[scooterscot]

Air pressure acts over our entire surface area (100,000 Newtons per metre squared, or around 10 thousand tonnes in weight per metre squared

Are we still talking about planet earth?

As for weight of the air above my head (assuming 1m^2) at surface level to atmosphere I could not possibly comment but I'm quite certain I'm not experiencing 10,000 tons of force on my shoulders.

[scooterscot]

Going back to the topic -

Why has no one invented a cylindrical piston yet? (i.e. a design where the crankshaft also becomes the pistons) It would take out the need for a crankshaft and piston rods, the system would be much more efficient as a result.

[TimberWolf]

Going back to the topic -

Why has no one invented a cylindrical piston yet? It would take out the need for a crankshaft and piston rods, the system would be much more efficient as a result.

Wankel engine? I gather electric motors are the way to go for efficiency. Unless the electricity is generated with a piston engine...

[VectraMan]

Going back to the topic -

Why has no one invented a cylindrical piston yet? (i.e. a design where the crankshaft also becomes the pistons) It would take out the need for a crankshaft and piston rods, the system would be much more efficient as a result.

That just sounds like it would be heavier with no gain. Or are you talking about a Wankel? Famous for their complete lack of efficiency (never understand why that is as it seems like it ought to be better).

[scooterscot]

I'm talking about the crankshaft where piston chambers are built as part of it, all incased in a manifold which would allow 1/4 revolution per spark. There would be only one moving part in this engine.

[Diver]

Okay, show that Archimedes principle is a consequence of the pressure differences on the surface of a submerged body. Extra marks will be awarded for using the words surface, cross-sectional or wetted area.

Boyles Law

PV = k

Where P is the pressure of gas,
V is the volume of gas
and k is a constant.

Boyle's law basically says that when you increase the pressure the volume decreases.
When you increase the volume the pressure decreases.

Charle's Law

Charles' Law states the relationship between temperature and volume of a gas at a constant pressure.

T/V = k

Where T is the temperature of a gas
V is the volume
and k is a constant

Charles' law states that cooling a gas decreases its volume.
If the volume is fixed then the pressure must decrease


Archimedes' principle

The principle is that the net (fluid) force on a body submerged (or floating) in a stationary fluid is an upward force equal to the weight of the fluid displaced.

0.445 Lbs per Sq Inch per foot for sea water, 0.433 Lbs per Sq inch per foot for Fresh water.

Archimedes’ law (Archimedes’ principle) states that a body, whether completely or partly submerged in a fluid, is buoyed upward by the force (buoyant force) that is equal to the weight of the displaced fluid.

Archimedes' principle is valid for submerged or floating bodies in liquids or gases

Diving at High altitude lakes etc. has caused many injuries and fatalities due the air pressure differential. Many divers have also encountered difficulty (injury) with embolism's (bends) when flying immediately or shortly after diving.

HTH

[TimberWolf]

Boyles Law

PV = k

Where P is the pressure of gas,
V is the volume of gas
and k is a constant.

Boyle's law basically says that when you increase the pressure the volume decreases.
When you increase the volume the pressure decreases.

Charle's Law

Charles' Law states the relationship between temperature and volume of a gas at a constant pressure.

T/V = k

Where T is the temperature of a gas
V is the volume
and k is a constant

Charles' law states that cooling a gas decreases its volume.
If the volume is fixed then the pressure must decrease


Archimedes' principle

The principle is that the net (fluid) force on a body submerged (or floating) in a stationary fluid is an upward force equal to the weight of the fluid displaced.

0.445 Lbs per Sq Inch per foot for sea water, 0.433 Lbs per Sq inch per foot for Fresh water.

Archimedes’ law (Archimedes’ principle) states that a body, whether completely or partly submerged in a fluid, is buoyed upward by the force (buoyant force) that is equal to the weight of the displaced fluid.

Archimedes' principle is valid for submerged or floating bodies in liquids or gases

Diving at High altitude lakes etc. has caused many injuries and fatalities due the air pressure differential. Many divers have also encountered difficulty (injury) with embolism's (bends) when flying immediately or shortly after diving.

HTH

User

Derive it from first principles - I thought you might be interested in the guts of it.

Incidentally :

Archimedes' principle is valid for submerged or floating bodies in liquids or gases

isn't always true since if a bottom surface isn't exposed to the pressure, there will be no buoyant force (excepting other convex or concave surfaces making up the shape of body). Makes thinking about bubbles stuck on the bottom of an underwater surface, etc interesting things to think about.

[DimPrawn]

This truly is the dullest thread CUK has ever seen.

Wilmslow, please come back!

[Diver]

User

Derive it from first principles - I thought you might be interested in the guts of it.

Incidentally :


isn't always true since if a bottom surface isn't exposed to the pressure, there will be no buoyant force (excepting other convex or concave surfaces making up the shape of body). Makes thinking about bubbles stuck on the bottom of an underwater surface, etc interesting things to think about.

Archimedes was asked to determine whether a crown made for King Heron II was made of pure gold.
He determined and demonstrated that the crown was not pure gold, because although the crown and a nugget of the same weight balanced on scales in air, they did not do so in water because the crown has a lower density than the nugget. <------Displacement see

Timberwolf - Incidentally :

Diver - Archimedes' principle is valid for submerged or floating bodies in liquids or gases

The law of displacement is still valid