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​ = 1 mmunloaded

A machine rests on spring mounts, which compress by 1 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 = 1 mmg = 9.81 m/s²
fn = Hz
2.Easy
k = 12 kN/mm = 10 kgx

A 10 kg mass hangs from a spring with a stiffness of 12 kN/m. Ignore damping. Find the natural circular frequency ωn in rad/s.

m = 10 kgk = 12 kN/m
ωn = rad/s
3.Medium
k = 5 kN/mζ = 0.35m = 50 kg

A 50 kg mass on a spring with a stiffness of 5 kN/m has a viscous damper giving a damping ratio of 0.35. Find the damped natural frequency fd of its free vibration in Hz.

m = 50 kgk = 5 kN/mζ = 0.35
fd = Hz
4.Medium
k = 100 kN/mζ = 0.4m = 250 kg

A 250 kg mass on a spring with a stiffness of 100 kN/m has a viscous damper giving a damping ratio of 0.4. Find the damped natural frequency fd of its free vibration in Hz.

m = 250 kgk = 100 kN/mζ = 0.4
fd = Hz
5.Hard
k1​ = 10k2​ = 5k3​ = 25m = 50 kg

A 50 kg mass hangs from spring k₃ = 25 kN/m. The top of k₃ is attached to a rigid bar that hangs from two springs side by side, k₁ = 10 kN/m and k₂ = 5 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 = 10 kN/mk2 = 5 kN/mk3 = 25 kN/m
fn = Hz
6.Hard
k1​ = 50k2​ = 50k3​ = 40m = 20 kg

A 20 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 = 50 kN/m and k₂ = 50 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 = 50 kN/mk2 = 50 kN/mk3 = 40 kN/m
fn = Hz

Answer key

  1. 1. fn = 15.76 Hz
  2. 2. ωn = 34.64 rad/s
  3. 3. fd = 1.491 Hz
  4. 4. fd = 2.917 Hz
  5. 5. fn = 2.179 Hz
  6. 6. fn = 6.015 Hz

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