Question

A mass of 5 kg is suspended from a spring of stiffness 46 kN/m. A dashpot is fitted between the mass and the support with a damping ratio of 0.3. Calculate the undamped frequency.

• A. 15.56 Hz
• B. 15.26 Hz
• C. 15.44 Hz
• D. 15.34 Hz

Answer 1

The correct option is B 15.26 Hz

The natural undamped frequency is given by
$f_n=\frac{1}{2\pi }\sqrt{\frac{k}{M}}\Rightarrow f_n=\frac{1}{2\pi }\sqrt{\frac{46000}{5}}=15.26Hz$