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​ = 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
2.Easy
k = 2 kN/mm = 10 kgx

A 10 kg mass hangs from a spring with a stiffness of 2 kN/m. Ignore damping. Find the natural frequency fn in Hz.

m = 10 kgk = 2 kN/m
fn = Hz
3.Medium
tx12 mm1 cycle6.4 mm

In a free-vibration test of a damped mass–spring system, a displacement peak of 12 mm is followed one cycle later by a peak of 6.4 mm. Find the damping ratio ζ.

x0 = 12 mmx1 = 6.4 mmn = 1
ζ =
4.Medium
k = 4 kN/mc = 340 N·s/mm = 20 kg

A 20 kg mass is supported by a spring with a stiffness of 4 kN/m and a viscous damper with a damping coefficient of 340 N·s/m. Find the damping ratio ζ.

m = 20 kgk = 4 kN/mc = 340 N·s/m
ζ =
5.Hard
k1​ = 12k2​ = 40m = 10 kg

A 10 kg mass hangs from two springs side by side (in parallel), with stiffnesses k₁ = 12 kN/m and k₂ = 40 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 = 10 kgk1 = 12 kN/mk2 = 40 kN/m
fn = Hz
6.Hard
k1​ = 50k2​ = 15m = 100 kg

A 100 kg mass hangs from two springs side by side (in parallel), with stiffnesses k₁ = 50 kN/m and k₂ = 15 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 = 100 kgk1 = 50 kN/mk2 = 15 kN/m
fn = Hz

Answer key

  1. 1. fn = 22.29 Hz
  2. 2. fn = 2.251 Hz
  3. 3. ζ = 0.09955
  4. 4. ζ = 0.601
  5. 5. fn = 11.48 Hz
  6. 6. fn = 4.058 Hz

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