Take the case of an air-filled balloon. You can tap the bottom of the balloon and it will rise up. But, it's heavier than the air around it (for two reasons). First, because it's the sum of the weights of the air and the latex of the balloon. Second, because the latex has an elasticity that needed to be overcome to blow the balloon up (in other words, the air in the balloon has more air pressure than that of the surrounding air).
in the same way you can throw a rock in the air, and it is certainly heavier than the air around it. the resultant in the differing rates of falling is the relative force able to be applied by the object.
In the case of a brick, there is a lot of mass for a relatively small surface area. this means that it is able to exert a lot of force per unit area of surface to displace the surrounding air. This means that it is able to undergo a larger acceleration when moving through the air with the only force being applied by gravity.
When we compare the relative surface area and mass with an air filled balloon hopefully you can see that a much smaller force is able to be exerted per unit area in comparison to the brick.
the reason why this is a factor in the rate of falling is that in order to move through a medium (such as air in this case) a force needs to be applied to displace the particles of the medium that it is falling through. When i think about this I can see that if you had two objects of the same shape/surface area, yet with differing masses, the object with the greatest mass will fall much quicker than the object with less mass.
This effect can be seen in many cases, such as dropping a feather in comparison to say a marble. The feather has a comparitively massive surface area relative to its mass, whilst a marble has the smallest possible surface area for it's mass. If you managed to find a marble and a feather that weighed the same you would see that the feather would fall slower than the marble.
But, the balloon doesn't just fall to the floor at a rate of 32 feet per second per second. It slowly sinks. Why? The balloon does have some buoyancy. It's difficult to imagine (at least for me it is), that there could be enough change of air pressure across the height of the balloon to significantly affect its buoyancy...but, there is. the air pushes up on the bottom of the balloon harder than it pushes down on the top.
But, what does it mean when you say that air is "pushing" on the balloon? It means that there is a force and a force implies energy and where's the energy in the air? Answer: it's in the heat that's moving the air molecules around.
I struggle to fathom your theory that buoyancy of a balloon is due to differing air pressure. At a standard sea level pressure there is approximately 1kg of force per square cm. According to you theory the reason a balloon floats is due to there being a greater pressure below the balloon than above the balloon.
However if you consider place a helium-filled balloon on the ground, assume that the is effectively no air below it. That would mean that it would only have the 1kg/cm force pushing down on the balloon. Surely if the differing pressure was the reason that the balloon floated, the balloon would never leave the ground as their would be a much greater force acting down on the balloon.
I agree however that the pressure exerted on the balloon is related directly to the temperature of the surrounding air. However pressure cannot be simply explained as the heat of the particles. If this were so, the change in number of particles per unit cubic area would have no effect on the pressure. However pressure is also most clearer dependent on the number of particles per unit cubic area.
Therefore pressure can be considered as dependent on temperature, however it does not consist of temperature. This is in the same way that kinetic energy is dependent on velocity not consisting of velocity.
I'm going to just ask a few clarifying questions.
Is it possible that "energy" can be defined as "mass in motion"? Some might invoke it as the conservation of matter and energy.
Energy itself is not mass in motion, however a mass in motion can do work, exert an energy due to its motion. Energy is not defined as mass in motion however a mass in motion has energy
I thought the classic definition of, "work" requires that something actually move. So, I'd ask two questions. First, is work being done when light shines on a wall (and pushes against it but, doesn't move it)? Second, if any object above absolute zero has thermal energy (moving molecules), is work being done all the time?
I hope we all can keep this moving forward and avoid getting into esoteric phenomena. I also hope that, in the back of our minds, we can keep the goal in sight of how this may all relate to how sound energy propagtes.
Work is most certainly being done when a light is shone on a wall. Whilst work can be defined as the force exerted times the distance, work is also the expenditure (change) of energy over time.
For the second part, if the absolute zero particle is still moving (for this to be remotely possible it would have to be in a vacuum all by it's lonesome... I can explain why if necessary) It still has energy due to its motion. However if this energy remains constant there is no work being done.
Work, I believe, is simply the exertion of energy.
I'm glad you said, "system" rather than "object". But, this doesn't define potential energy. It just comments on it. what is it about that system that stores that energy?
The system allows energy to be stored in such a way that it is able to be released at a later point. I know this is pretty much exactly what I said before. lets look at some specifics.
gravitational potential is the potential energy of an object due to the gravitational force that can be exerted on it. I like my pencil up and it has gravitational potential energy, as when there is no restoring force (force upwards provided by my hand), It gains energy due to gravity.
In an elastic potential system, i stretch a rubber band with my hands. The forces between the molecules in the rubber band wish to be at the smallest possible energy level, i.e. molecules as close together such that the attraction betweens molecules is equal to the repulsion. When I have stretched the band, I have put energy into the system. I have lengthened the bonds between the molecules by putting extra energy into them. If my hands were not applying a force to keep it stretched, the molecules within the rubber band would attract each other back to the minimal energy configuration.
In fact when I do release the restoring force (my hands), the bonds attractions between the molecules pull the molecules back closer together. the extra energy that was in these bonds are released, partially in kinetic energy (the molecules moving back together, or perhaps a witty projectile) sound and loss of heat.
There are other sorts including chemical that I can go into if desired.
Actually, some of the pressure does leak away as heat (conversely, on the next hot day, or after a drive, it can also be put back...as heat).
Why doesn't all the pressure leak away as heat? Well, because, after pumping up the tire and some of the energy of compressing the air leaks away, the tire reaches an equilibrium where it's absorbing and radiating/conducting the same amount of heat and so the pressure also stabinlizes.
one last thing, i really don't like the way that you say pressure is leaked away. It's true that there is a change in pressure, but you can't just get a can of pressure and pump it into the system (well actually..... I suppose you can in a way....).
The reason for a change in pressure is the relative force applied to the tyre from the inside. This average force is dependent on the number of collisions of molecules with the tyre per second (partly dictated by the nu,ber of particles per unit cubic area) and then also the forve applied in each of these collisions (hey there is the heat energy of the particles)
As the particles lose or gain heat energy the pressure changes accordingly, also rather self explanitorily as the tyre loses or gains gaseous molecules the pressure changes. In this way you are correct in that a tyres reaches and equilibrium at which point the heat energy is the same.
anyways I have to go now... will discuss more later