Mechanical vibrations worksheet with answers

Free printable Mechanical vibrations worksheet: 6 problems from easy to exam level, with an answer key. Print it or save it as a PDF.

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1.Easy

An 8 kg mass hangs from a spring with a stiffness of 20 kN/m. Ignore damping. Find the natural frequency f_n in Hz.

m = 8 kgk = 20 kN/m

f_n = Hz

2.Easy

A 5 kg mass hangs from a spring with a stiffness of 25 kN/m. Ignore damping. Find the natural frequency f_n in Hz.

m = 5 kgk = 25 kN/m

f_n = Hz

3.Medium

A 12 kg mass on a spring with a stiffness of 5 kN/m has a viscous damper giving a damping ratio of 0.6. Find the damped natural frequency f_d of its free vibration in Hz.

m = 12 kgk = 5 kN/mζ = 0.6

f_d = Hz

4.Medium

A 250 kg mass is supported by a spring with a stiffness of 200 kN/m and a viscous damper with a damping coefficient of 8490 N·s/m. Find the damping ratio ζ.

m = 250 kgk = 200 kN/mc = 8490 N·s/m

ζ =

5.Hard

A 5 kg mass hangs from spring k₃ = 60 kN/m. The top of k₃ is attached to a rigid bar that hangs from two springs side by side, k₁ = 60 kN/m and k₂ = 80 kN/m; the bar stays level. Ignore damping and the masses of the springs and bar. Find the natural frequency f_n of vertical vibration in Hz.

m = 5 kgk₁ = 60 kN/mk₂ = 80 kN/mk₃ = 60 kN/m

f_n = Hz

6.Hard

A 5 kg mass hangs from two springs connected end to end (in series): the upper spring has k₁ = 60 kN/m and the lower one k₂ = 40 kN/m. Find the equivalent stiffness k_eq of the spring system in kN/m.

m = 5 kgk₁ = 60 kN/mk₂ = 40 kN/m

k_eq = kN/m

Answer key

1. f_n = 7.958 Hz
2. f_n = 11.25 Hz
3. f_d = 2.599 Hz
4. ζ = 0.6003
5. f_n = 14.59 Hz
6. k_eq = 24 kN/m

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