levitation

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     "source": "# levitating a stone\n\nRoksana Pirouzmand, 10/2/2013\n\nI want to levitate a large stone in a gallery. Air blowing on the stone from below will provide the force to keep it from falling to the floor of the gallery. How much force will the air need to exert? Does such a fan exist?\n\n1. Calculate the force needed to hold the rock up (this is the inverse of gravity)\n2. calculate the terminal velocity for the stone. This is a good approximation of how much air pressure will be needed to hold the rock steady. \n\nThis is simpler than it seemed, assuming that the terminal velocity is calculable.\n\n> When an object which is falling under the influence of gravity or subject to some other constant driving force is subject to a resistance or drag force which increases with velocity, it will ultimately reach a maximum velocity where the drag force equals the driving force. This final, constant velocity of motion is called a \"terminal velocity\", a terminology made popular by skydivers. For objects moving through a fluid at low speeds so that turbulence is not a major factor, the terminal velocity is determined by viscous drag. The expression for the terminal velocity is of the form:\n\n![](http://hyperphysics.phy-astr.gsu.edu/hbase/fluids/imgflu/linf6.gif)\n\nObjects moving at high speeds through air encounter air drag proportional to the square of the velocity. This quadratic drag leads to a terminal velocity of the form:\n\n![](http://hyperphysics.phy-astr.gsu.edu/hbase/fluids/imgflu/linf7.gif)\n\n**Terminal Velocity Examples**\n\n| Falling object | Mass | Area | Terminal velocity in meters/sec | mph |\n|:-------------- |:-------- |:----------------- |\n| Skydiver| 75 kg| 0.7 m2 | 60 m/s | 134 mi/hr |\n| Baseball (3.66cm radius) | 145 gm | 42 cm2 | 33 m/s | 74 mi/hr |\n| Golf ball (2.1 cm radius) | 46 gm | 14 cm2 | 32 m/s | 72 mi/hr |\n| Hail stone (0.5 cm radius) | .48 gm | .79 cm2 | 14 m/s | 31 mi/hr |\n| Raindrop (0.2 cm radius) | .034 gm | .13 cm2 | 9 m/s | 20 mi/hr |\n\n\n# speculation\nA question emerged through our discussion about the linkage between the objects held up by the air and the source of the air pressure. \n\nImagine a blow dryer linked to a scale. At rest the dryer weights one kg. When activated, the force of the displaced air is conveyed to the scale and it now reads 1.5kg. \n\nNow, start putting objects into the stream of air. Does the \"weight\" indicator on the scale change as objects are added?\n\n\n## statement\n\n**the weight indicated on the scale would not increase as objects were placed in the stream of air.**  \n\nLeading to a falsifiable statement:\n\n**Weight indicated on the scale will not be changed by adding objects to the stream.**\n\n\nthe object is held aloft by the difference between the high and low pressures on the close and far sides of the stone relative to the movement of or in air. \n\nThere are other effects. Importantly the convection of the air current and the size and shape of the jet. We should look at jet engines and turbines more carefully because this project will likely need a jet engine of some kind. Imagine a fireworks rocket with a replenishible fuel supply.\n\nWe also discussed how jet engines produce force, how fast skydivers feel that they are falling (and the relative slowdowns and accelerations that may be achieved by opening the arms / pointing into the wind)\n\n**references**\n\n* [Terminal Velocity](http://hyperphysics.phy-astr.gsu.edu/hbase/airfri2.html)\n* [High pressure fan image search](https://encrypted.google.com/search?tbm=isch&q=high%20pressure%20fan)"
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     "source": "1. mass of the stone\n1. force of gravity 32 ft/sec /sec\n1. terminal velocity? compare space\n1. is it dependant on sirface area?\n1. to calculate where the stone would be in 4 secs, f=ma where a = gravity\n1. how much total air resistance?\n1. how it turn? dependant on air resistance or mass"
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     "source": "1. does the size of the room matter?\n1. what is the maximum pressure that can be exerted?\n1. jet engine?\n1. spinning the air--would convestion matter?\n1. would increasing the pressure in a stream by narrowing it matter?\n1. does density matter?  what's the relationship to lift?\n1. what is the relationship of density between the rock and the \n1. is there an optimal distance between the rock and the air? \n1. air prossure and the terminal velocity?\n1. dos the convection matter? compare tornado"
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     "source": "let's determin if the fan and the stone are coupled. \n\nplace a fan on a scal. turn it on. measure the force applied to the scale before and after the fan is running. "
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