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​ = 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
2.Easy
k = 40 kN/mm = 200 kgx

A 200 kg mass hangs from a spring with a stiffness of 40 kN/m. Ignore damping. Find the natural circular frequency ωn in rad/s.

m = 200 kgk = 40 kN/m
ωn = rad/s
3.Medium
k = 10 kN/mc = 220 N·s/mm = 20 kg

A 20 kg mass is supported by a spring with a stiffness of 10 kN/m and a viscous damper with a damping coefficient of 220 N·s/m. Find the damping ratio ζ.

m = 20 kgk = 10 kN/mc = 220 N·s/m
ζ =
4.Medium
k = 200 kN/mc = 1580 N·s/mm = 50 kg

A 50 kg mass is supported by a spring with a stiffness of 200 kN/m and a viscous damper with a damping coefficient of 1580 N·s/m. Find the damping ratio ζ.

m = 50 kgk = 200 kN/mc = 1580 N·s/m
ζ =
5.Hard
k1​ = 5k2​ = 12m = 50 kg

A 50 kg mass hangs from two springs side by side (in parallel), with stiffnesses k₁ = 5 kN/m and k₂ = 12 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 = 50 kgk1 = 5 kN/mk2 = 12 kN/m
fn = Hz
6.Hard
k1​ = 80k2​ = 12k3​ = 12m = 10 kg

A 10 kg mass hangs from spring k₃ = 12 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 = 12 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 = 12 kN/mk3 = 12 kN/m
fn = Hz

Answer key

  1. 1. fn = 7.882 Hz
  2. 2. ωn = 14.14 rad/s
  3. 3. ζ = 0.246
  4. 4. ζ = 0.2498
  5. 5. fn = 2.935 Hz
  6. 6. fn = 5.185 Hz

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