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
kmδst​ = 1 mmunloaded

A machine rests on spring mounts, which compress by 1 mm under its weight. Treat it as an undamped single-degree-of-freedom system and use g = 9.81 m/s². Find the natural frequency fn of vertical vibration in Hz.

δst = 1 mmg = 9.81 m/s²
fn = Hz
2.Easy
kmδst​ = 20 mmunloaded

A machine rests on spring mounts, which compress by 20 mm under its weight. Treat it as an undamped single-degree-of-freedom system and use g = 9.81 m/s². Find the natural frequency fn of vertical vibration in Hz.

δst = 20 mmg = 9.81 m/s²
fn = Hz
3.Medium
k = 5 kN/mζ = 0.5m = 20 kg

A 20 kg mass on a spring with a stiffness of 5 kN/m has a viscous damper giving a damping ratio of 0.5. Find the damped natural frequency fd of its free vibration in Hz.

m = 20 kgk = 5 kN/mζ = 0.5
fd = Hz
4.Medium
k = 12 kN/mc = 100 N·s/mm = 5 kg

A 5 kg mass is supported by a spring with a stiffness of 12 kN/m and a viscous damper with a damping coefficient of 100 N·s/m. Find the damping ratio ζ.

m = 5 kgk = 12 kN/mc = 100 N·s/m
ζ =
5.Hard
k1​ = 10k2​ = 12m = 25 kg

A 25 kg mass hangs from two springs side by side (in parallel), with stiffnesses k₁ = 10 kN/m and k₂ = 12 kN/m. The mass stays level. Find the equivalent stiffness keq of the spring system in kN/m.

m = 25 kgk1 = 10 kN/mk2 = 12 kN/m
keq = kN/m
6.Hard
k1​ = 25k2​ = 25m = 40 kg

A 40 kg mass hangs from two springs connected end to end (in series): the upper spring has k₁ = 25 kN/m and the lower one k₂ = 25 kN/m. Find the equivalent stiffness keq of the spring system in kN/m.

m = 40 kgk1 = 25 kN/mk2 = 25 kN/m
keq = kN/m

Answer key

  1. 1. fn = 15.76 Hz
  2. 2. fn = 3.525 Hz
  3. 3. fd = 2.179 Hz
  4. 4. ζ = 0.2041
  5. 5. keq = 22 kN/m
  6. 6. keq = 12.5 kN/m

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