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​ = 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
2.Easy
kmδst​ = 0.5 mmunloaded

A machine rests on spring mounts, which compress by 0.5 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 = 0.5 mmg = 9.81 m/s²
fn = Hz
3.Medium
tx30 mm5 cycles6.2 mm

In a free-vibration test of a damped mass–spring system, a displacement peak of 30 mm is followed 5 cycles later by a peak of 6.2 mm. Find the damping ratio ζ.

x0 = 30 mmx5 = 6.2 mmn = 5
ζ =
4.Medium
k = 15 kN/mc = 460 N·s/mm = 10 kg

A 10 kg mass is supported by a spring with a stiffness of 15 kN/m and a viscous damper with a damping coefficient of 460 N·s/m. Find the damping ratio ζ.

m = 10 kgk = 15 kN/mc = 460 N·s/m
ζ =
5.Hard
k1​ = 100k2​ = 15k3​ = 20m = 20 kg

A 20 kg mass hangs from spring k₃ = 20 kN/m. The top of k₃ is attached to a rigid bar that hangs from two springs side by side, k₁ = 100 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 = 20 kgk1 = 100 kN/mk2 = 15 kN/mk3 = 20 kN/m
fn = Hz
6.Hard
k1​ = 5k2​ = 15k3​ = 80m = 50 kg

A 50 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 = 5 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 = 50 kgk1 = 5 kN/mk2 = 15 kN/mk3 = 80 kN/m
fn = Hz

Answer key

  1. 1. fn = 3.525 Hz
  2. 2. fn = 22.29 Hz
  3. 3. ζ = 0.05012
  4. 4. ζ = 0.5939
  5. 5. fn = 4.645 Hz
  6. 6. fn = 2.847 Hz

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