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 mmunloaded

A machine rests on spring mounts, which compress by 2 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 mmg = 9.81 m/s²
fn = Hz
2.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
3.Medium
k = 100 kN/mζ = 0.4m = 10 kg

A 10 kg mass on a spring with a stiffness of 100 kN/m has a viscous damper giving a damping ratio of 0.4. Find the damped natural frequency fd of its free vibration in Hz.

m = 10 kgk = 100 kN/mζ = 0.4
fd = Hz
4.Medium
k = 25 kN/mζ = 0.6m = 200 kg

A 200 kg mass on a spring with a stiffness of 25 kN/m has a viscous damper giving a damping ratio of 0.6. Find the damped natural frequency fd of its free vibration in Hz.

m = 200 kgk = 25 kN/mζ = 0.6
fd = Hz
5.Hard
k1​ = 80k2​ = 80m = 5 kg

A 5 kg mass hangs from two springs side by side (in parallel), with stiffnesses k₁ = 80 kN/m and k₂ = 80 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 = 5 kgk1 = 80 kN/mk2 = 80 kN/m
fn = Hz
6.Hard
k1​ = 5k2​ = 25m = 5 kg

A 5 kg mass hangs from two springs connected end to end (in series): the upper spring has k₁ = 5 kN/m and the lower one k₂ = 25 kN/m. Find the equivalent stiffness keq of the spring system in kN/m.

m = 5 kgk1 = 5 kN/mk2 = 25 kN/m
keq = kN/m

Answer key

  1. 1. fn = 11.15 Hz
  2. 2. fn = 9.97 Hz
  3. 3. fd = 14.59 Hz
  4. 4. fd = 1.424 Hz
  5. 5. fn = 28.47 Hz
  6. 6. keq = 4.167 kN/m

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