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​ = 2.5 mmunloaded

A machine rests on spring mounts, which compress by 2.5 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 = 2.5 mmg = 9.81 m/s²
fn = Hz
2.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
3.Medium
k = 4 kN/mc = 20 N·s/mm = 10 kg

A 10 kg mass is supported by a spring with a stiffness of 4 kN/m and a viscous damper with a damping coefficient of 20 N·s/m. Find the damping ratio ζ.

m = 10 kgk = 4 kN/mc = 20 N·s/m
ζ =
4.Medium
k = 10 kN/mc = 450 N·s/mm = 20 kg

A 20 kg mass is supported by a spring with a stiffness of 10 kN/m and a viscous damper with a damping coefficient of 450 N·s/m. Find the damping ratio ζ.

m = 20 kgk = 10 kN/mc = 450 N·s/m
ζ =
5.Hard
k1​ = 80k2​ = 20m = 20 kg

A 20 kg mass hangs from two springs side by side (in parallel), with stiffnesses k₁ = 80 kN/m and k₂ = 20 kN/m. The mass stays level. Ignore damping and the masses of the springs. Find the natural frequency fn of vertical vibration in Hz.

m = 20 kgk1 = 80 kN/mk2 = 20 kN/m
fn = Hz
6.Hard
k1​ = 100k2​ = 50m = 20 kg

A 20 kg mass hangs from two springs connected end to end (in series): the upper spring has k₁ = 100 kN/m and the lower one k₂ = 50 kN/m. Find the equivalent stiffness keq of the spring system in kN/m.

m = 20 kgk1 = 100 kN/mk2 = 50 kN/m
keq = kN/m

Answer key

  1. 1. fn = 9.97 Hz
  2. 2. fn = 15.76 Hz
  3. 3. ζ = 0.05
  4. 4. ζ = 0.5031
  5. 5. fn = 11.25 Hz
  6. 6. keq = 33.33 kN/m

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