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Question 11 5 points Save Arswer A wayward youth pulls back and releases a car radio aerial parallel to ground. The aerial has a length 64 cm and a small mass 22 g at its tip. The mass is released from a point 14 cm from the aerial equilibrium point. After 3 complete oscillations the peak displacement is 2 cm. Assuming the aerial is a massless beam with a Yougns' Modulus E = 69 Gpa, and a second moment of area 4.1x10-6 m, use the log decrement to find the correct damping coefficient, c, of the aerial in Ns/m. W kefsic E, L m Xo O A. 27.6 N/m B. 55.1 Ns/m C. 82.7 Ns/m D. 110.2 NS/M E. 165.3 Ns/m F. 1742.5 Ns/m Question 12 5 points Save Answer The DOF vibration system below is subjected to a sinusoidal forced vibration of unknown magnitude over a broad range of frequencies. You observe the peak amplitude of vibration to be x = 0.05 m. Calculate the magnitude of the force acting upon the system in Newtons assuming a spring constant k = 11 N/m and a damping ratio of <= 0.05. Calculate your answer to two decimal places. +x(t) ning m F(t) Question 13 5 points Save Answer The damping coefficient of a table-top vibration isolation platform is being tuned & tested on a shaking table. The mass of the table-top platform is 14 kg but has an unknown spring constant. The Transmissibility of the table-top platform is tested over a range of frequencies for 2 different platform camping coefficients. The Transmissibility is shown to be equal to unity for the 2 different damping coefficients at a single frequency: 1.4 H2. From this observation calculate the critical damping coefficient of the system. Give your answer to the nearest N.s/m. C 1 C2 T=1 Yout Isolation platform m Zk C1, C2 T, I-1 Yin Vibration table 0 0 0.5 1 2 2.5 3 1.5 r. [-]
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