Dragging a 2 sq. inch item through the water behind a boat, what would the psi be on that item at each of 10 mph increment from 10 mph to 100 mph. (We know many factors will affect this (salinity, current, barom etric pressure, altitude, etc.), but only a reasonable approximation is needed).
It depends a lot on the shape of the object: a cone will move easier than a flat surface. if the flow is laminar - meaning there are no vortexex around the object as it moves - the resistance increases with the third power of the speed.
Hence if you are able to measure 5psi at 10mph, you could predict that you will have 5*2^3 = 40psi at 20mph, and 5*3^3 = 135psi at 30mph. At higher speeds the flow will become non-laminar, and this will increase the resistance even faster as we increase the speed.
There are no simple formulas, but some calculations can be made - this is the field of fluid dynamics. Any matter of practical consequence needs to be tested in wind tunnels or water pools, using rather sophisticated measuring tools and scale models.
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