If the screen width is 7 feet and the projector's throw ratio is 2.0 - 2.4:1 (because projectors have zoom lenses, they also have a range of throw ratios) then you can place your projector anywhere from 14 to 16.8 feet away from the screen.
A strain gauge (or strain gage) is a device used to measure strain on an object. Invented by Edward E. Simmons and Arthur C. Ruge in 1938, the most common type of strain gauge consists of an insulating flexible backing which supports a metallic foil pattern.he gauge is far more sensitive to strain in the vertical direction than in the horizontal direction.
From engineering to true strain, true stress. First of all, you may check that your experimental data from a uniaxial tension test is expressed in terms of true stress vs. true strain, not engineering stress or strain. True strain = ln(1 + engineering strain) where ln designates the natural log.