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In a theoretically perfect situation with weightless spheres, a "vacuum balloon" would have 7% more net lifting force than a hydrogen-filled balloon, and 16% more net lifting force than a helium-filled one. However, because the walls of the balloon must remain rigid without imploding, the balloon is impractical to construct with any known material.
A vacuum airship, also known as a vacuum balloon, is a hypothetical airship that is evacuated rather than filled with a lighter-than-air gas such as hydrogen or helium. First proposed by Italian Jesuit priest Francesco Lana de Terzi in 1670, [ 1 ] the vacuum balloon would be the ultimate expression of lifting power per volume displaced.
Suppose that, when the rock is lowered into the water, it displaces water of weight 3 newtons. The force it then exerts on the string from which it hangs would be 10 newtons minus the 3 newtons of buoyant force: 10 − 3 = 7 newtons. Buoyancy reduces the apparent weight of objects that have sunk completely to the sea-floor.
It is unclear how strong a vacuum Guericke's pump was able to achieve, but if it was able to evacuate all of the air from the inside, the hemispheres would have been held together with a force of around 20 kilonewtons (4,500 lbf; 2.2 short tons-force), [7] [8] equivalent to lifting a car or small elephant; a dramatic demonstration of the ...
He would dip a glass tube, closed at one end, into a bowl of mercury and raise the closed end out of it, keeping the open end submerged. The weight of the mercury would pull it down, leaving a partial vacuum at the far end. This validated his belief that air/gas has mass, creating pressure on things around it.
Bernoulli's principle can be used to calculate the lift force on an airfoil, if the behaviour of the fluid flow in the vicinity of the foil is known. For example, if the air flowing past the top surface of an aircraft wing is moving faster than the air flowing past the bottom surface, then Bernoulli's principle implies that the pressure on the ...
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Water vapor can also be indirect evidence supporting the presence of extraterrestrial liquid water in the case of some planetary mass objects. Water vapor, which reacts to temperature changes, is referred to as a 'feedback', because it amplifies the effect of forces that initially cause the warming. Therefore, it is a greenhouse gas. [2]