Exercise E2.4 used a natural vibration frequency to measure the modulus of a beam. Use the information in E2.4 to calculate the density of the beam, and then use this and the result of the exercise (the modulus of the beam) as a forensic tool. Scan the modulus values in Table A3 of Appendix A seeking a match between the calculated modulus and those in the table. What subsets of materials match the calculated modulus? Of these, which subset also matches the calculated density?

Data From Exercise E2.4

Data From Appendix Table A3

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E2.4. Vibration of beams. A cantilever beam with length Z=200 mm, width b=12 mm and thickness -2 mm weighs 38 grams and has a natural vibration frequency of f=42 hertz. What is the modulus of the material of the beam? You will find equations for natural frequencies of vibration and moments of area in Appendix B, Tables B12 and B2. L- FIGURE E2.4