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.

For teachers: free to print, copy and use in class. Every new worksheet has new values and its own answer key. A link to ExamProblems on your course page is appreciated.

Name: ____________________   Date: ____________

1.Easy
kmδst​ = 25 mmunloaded

A machine rests on spring mounts, which compress by 25 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 = 25 mmg = 9.81 m/s²
fn = Hz
2.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
3.Medium
k = 1 kN/mc = 10 N·s/mm = 2 kg

A 2 kg mass is supported by a spring with a stiffness of 1 kN/m and a viscous damper with a damping coefficient of 10 N·s/m. Find the damping ratio ζ.

m = 2 kgk = 1 kN/mc = 10 N·s/m
ζ =
4.Medium
tx20 mm1 cycle10.6 mm

In a free-vibration test of a damped mass–spring system, a displacement peak of 20 mm is followed one cycle later by a peak of 10.6 mm. Find the damping ratio ζ.

x0 = 20 mmx1 = 10.6 mmn = 1
ζ =
5.Hard
k1​ = 40k2​ = 10m = 100 kg

A 100 kg mass hangs from two springs side by side (in parallel), with stiffnesses k₁ = 40 kN/m and k₂ = 10 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 = 40 kN/mk2 = 10 kN/m
fn = Hz
6.Hard
k1​ = 20k2​ = 80m = 20 kg

A 20 kg mass hangs from two springs connected end to end (in series): the upper spring has k₁ = 20 kN/m and the lower one k₂ = 80 kN/m. Find the equivalent stiffness keq of the spring system in kN/m.

m = 20 kgk1 = 20 kN/mk2 = 80 kN/m
keq = kN/m

Answer key

  1. 1. fn = 3.153 Hz
  2. 2. fn = 4.551 Hz
  3. 3. ζ = 0.1118
  4. 4. ζ = 0.1005
  5. 5. fn = 3.559 Hz
  6. 6. keq = 16 kN/m

Full step-by-step solutions: practise this topic on examproblems.com.