Problem 15 A \( 350 \mathrm{~kg} \) mass, constrained to move only vertically, is supported by two springs, each having a spring constant of \( 250 \mathrm{kN} / \mathrm{m} \). A periodic force with a maximum value of \( 100 \mathrm{~N} \) is applied to the mass with a frequency of \( 2.5 \mathrm{rad} / \mathrm{s} \). Given a damping factor of 0.125 , the amplitude of the vibration is (A) \( 0.198 \mathrm{~mm} \) (B) \( 0.199 \mathrm{~mm} \) (C) \( 0.201 \mathrm{~mm} \) (D) \( 0.404 \mathrm{~mm} \)

Solution Calculate the total spring constant.