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​ = 12 mmunloaded

A machine rests on spring mounts, which compress by 12 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 = 12 mmg = 9.81 m/s²
fn = Hz
2.Easy
kmδst​ = 4 mmunloaded

A machine rests on spring mounts, which compress by 4 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 = 4 mmg = 9.81 m/s²
fn = Hz
3.Medium
k = 40 kN/mc = 390 N·s/mm = 15 kg

A 15 kg mass is supported by a spring with a stiffness of 40 kN/m and a viscous damper with a damping coefficient of 390 N·s/m. Find the damping ratio ζ.

m = 15 kgk = 40 kN/mc = 390 N·s/m
ζ =
4.Medium
k = 15 kN/mc = 550 N·s/mm = 20 kg

A 20 kg mass is supported by a spring with a stiffness of 15 kN/m and a viscous damper with a damping coefficient of 550 N·s/m. Find the damping ratio ζ.

m = 20 kgk = 15 kN/mc = 550 N·s/m
ζ =
5.Hard
k1​ = 20k2​ = 40k3​ = 40m = 100 kg

A 100 kg mass hangs from spring k₃ = 40 kN/m. The top of k₃ is attached to a rigid bar that hangs from two springs side by side, k₁ = 20 kN/m and k₂ = 40 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 = 100 kgk1 = 20 kN/mk2 = 40 kN/mk3 = 40 kN/m
fn = Hz
6.Hard
k1​ = 50k2​ = 15m = 40 kg

A 40 kg mass hangs from two springs connected end to end (in series): the upper spring has k₁ = 50 kN/m and the lower one k₂ = 15 kN/m. Ignore damping and the masses of the springs. Find the natural frequency fn of vertical vibration in Hz.

m = 40 kgk1 = 50 kN/mk2 = 15 kN/m
fn = Hz

Answer key

  1. 1. fn = 4.551 Hz
  2. 2. fn = 7.882 Hz
  3. 3. ζ = 0.2517
  4. 4. ζ = 0.5021
  5. 5. fn = 2.466 Hz
  6. 6. fn = 2.703 Hz

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