Please explain to us heretics how 2 scalar quantities (external pressure and internal pressure) combine to create a vector quantity?
https://www.khanacademy.org/science/chemistry/thermodynamics-chemistry/internal-energy-sal/a/pressure-volume-work
Slow learner aintcha Geoff?
Oh dear, this didn't start well for you, isn't going well, and it ain't gonna end well!
Your link goes to the page on Thermodynamics and Work, using the equation work=−PΔV.
But Poppy, pressure, volume and work or all scalar! Which is sad for Poppa-Fhysics!!TM, but does add some extra heat into the roasted nuts.
So, for the gazillionth time (I know, I'm exaggerating), please do explain, how 2 scalar quantities combine to produce a vector quantity, specifically how external pressure (scalar) and internal pressure (scalar) combine to produce an "unbalanced force" (shall we call that, errr, thrust - a vector quantity)?
Now, I know you won't (can't), and you know you won't (can't), and everyone else reading this thread knows you won't (can't), but holding your feet to the fire just adds to the fun Poppy!
Just so we know where we're at, according to
Poppa-Fhysics!!TM:-
The First Law of
Poppa-Fhysics!!TM:
An unbalanced force can only be created when the internal pressure created by the rocket engine meets an external pressure.Let's chew on that one for a while... an internal pressure 'meets' an external pressure, and creates an 'unbalanced force'.
Presumably, according to
Poppa-Fhysics!!TM, if the internal pressure is the same as the external pressure, then there is no unbalanced force, so the rocket doesn't move? By the same rationale, can we make the assumption that as we increase the pressure inside the rocket engine, the unbalanced force increases in direct proportion to the difference between the internal and external pressures? Sounds reasonable.
Thought experiment. What happens if we increase the pressure inside the rocket engine, by burning fuel and oxidiser? Pressure inside combustion chamber is very high, pressure outside is 1 Atmosphere. By the First Law, this creates an unbalanced force, and the rocket lifts off. Sounds reasonable.
So, our rocket reaches the heady heights of 1000 feet above sea level. The pressure in the rocket is pretty much constant (we're burning fuel and oxidiser at the same rate), but atmospheric pressure has dropped slightly. By the First Law of
Poppa-Fhysics!!TM, this
increases the unbalanced force, providing greater thrust on the rocket.
This process continues, with our imaginary rocket getting higher and higher, the atmospheric pressure getting lower and lower, and the unbalanced force gradually getting higher in proportion to the pressure difference, until... at some notional height, to be explained by Poppa, the number of atmospheric molecules per cubic metre goes from 5, to 4, 3, 2, 1... OK, still an atmosphere, so now our highest level of thrust yet... aaaand, zero molecules per cubic metre, perfect vacuum, aaaaaand, the balanced force magically disappears, the level of thrust instantly drops to zero, and our plucky little rocket plummets back to earth.
Now, I predict Poppy's counter argument will go one of two ways:
Firstly, he might claim that the unbalanced force actually gets SMALLER as the pressure difference increases (which is counter to the First Law of
Poppa-Fhysics!!TMm since if the pressures are the same, there is no unbalanced force.
Secondly, he will just post some psychobabble and ignore the post!
I vote for option 2. After all,
Total silence from Poppy in the face of even the slightest opposition = An action typical of cowards & bullies btw.
Strudels!
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