A circular disk is hung in an air stream from a pivoted strut as shown. In a wind-tunnel experiment, performed in air at \(15 \mathrm{~m} / \mathrm{s}\) with a \(25-\mathrm{mm}\) diameter disk, \(\alpha\) was measured at \(10^{\circ}\). For these conditions determine the mass of the disk. Assume the drag coefficient for the disk applies when the component of wind speed normal to the disk is used. Assume drag on the strut and friction in the pivot are negligible. Plot a theoretical curve of \(\alpha\) as a function of air speed.

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L P9.92 V