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​ = 8 mmunloaded

A machine rests on spring mounts, which compress by 8 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 = 8 mmg = 9.81 m/s²
fn = Hz
2.Easy
kmδst​ = 10 mmunloaded

A machine rests on spring mounts, which compress by 10 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 = 10 mmg = 9.81 m/s²
fn = Hz
3.Medium
k = 10 kN/mζ = 0.5m = 80 kg

An 80 kg mass on a spring with a stiffness of 10 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 = 80 kgk = 10 kN/mζ = 0.5
fd = Hz
4.Medium
tx40 mm2 cycles8.8 mm

In a free-vibration test of a damped mass–spring system, a displacement peak of 40 mm is followed 2 cycles later by a peak of 8.8 mm. Find the damping ratio ζ.

x0 = 40 mmx2 = 8.8 mmn = 2
ζ =
5.Hard
k1​ = 25k2​ = 25m = 10 kg

A 10 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. Ignore damping and the masses of the springs. Find the natural frequency fn of vertical vibration in Hz.

m = 10 kgk1 = 25 kN/mk2 = 25 kN/m
fn = Hz
6.Hard
k1​ = 80k2​ = 15k3​ = 80m = 10 kg

A 10 kg mass hangs from spring k₃ = 80 kN/m. The top of k₃ is attached to a rigid bar that hangs from two springs side by side, k₁ = 80 kN/m and k₂ = 15 kN/m; the bar stays level. Ignore damping and the masses of the springs and bar. Find the natural frequency fn of vertical vibration in Hz.

m = 10 kgk1 = 80 kN/mk2 = 15 kN/mk3 = 80 kN/m
fn = Hz

Answer key

  1. 1. fn = 5.573 Hz
  2. 2. fn = 4.985 Hz
  3. 3. fd = 1.541 Hz
  4. 4. ζ = 0.1196
  5. 5. fn = 5.627 Hz
  6. 6. fn = 10.49 Hz

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