If for some viscoelastic polymer, the stress decays over time and follows the equation σ(t)=σ(0)exp(-t/τ), (equation 15.10). determine the relaxation modulus at 15s if the initial stress was 3mpa, the intial strain was 0.5 and the relaxation time is 20s.

An engine, weighing 3000 n, is supported on a pedestal mount. it has been observed that the engine induces vibration into the surrounding area through its pedestal at the maximum operating speed. determine the stiffness of the dynamic vibration absorber spring in (n/m) that will reduce the vibration when mounted on the pedestal. the magnitude of the exciting force is 250 n, and the amplitude of motion of the auxiliary mass is to be limited to 2 mm note: in this question type-in right numbers, no decimals, no fractions, no unit. approximate to right number if needed