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

A 15 kg mass hangs from a spring with a stiffness of 150 kN/m. Ignore damping. Find the natural frequency f_n in Hz.

m = 15 kgk = 150 kN/m

f_n = Hz

2.Easy

A 50 kg mass hangs from a spring with a stiffness of 150 kN/m. Ignore damping. Find the natural frequency f_n in Hz.

m = 50 kgk = 150 kN/m

f_n = Hz

3.Medium

In a free-vibration test of a damped mass–spring system, a displacement peak of 15 mm is followed 5 cycles later by a peak of 0.6 mm. Find the damping ratio ζ.

x₀ = 15 mmx₅ = 0.6 mmn = 5

ζ =

4.Medium

In a free-vibration test of a damped mass–spring system, a displacement peak of 20 mm is followed 3 cycles later by a peak of 11.4 mm. Find the damping ratio ζ.

x₀ = 20 mmx₃ = 11.4 mmn = 3

ζ =

5.Hard

A 100 kg mass hangs from spring k₃ = 10 kN/m. The top of k₃ is attached to a rigid bar that hangs from two springs side by side, k₁ = 25 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 f_n of vertical vibration in Hz.

m = 100 kgk₁ = 25 kN/mk₂ = 40 kN/mk₃ = 10 kN/m

f_n = Hz

6.Hard

A 50 kg mass hangs from two springs side by side (in parallel), with stiffnesses k₁ = 30 kN/m and k₂ = 40 kN/m. The mass stays level. Find the equivalent stiffness k_eq of the spring system in kN/m.

m = 50 kgk₁ = 30 kN/mk₂ = 40 kN/m

k_eq = kN/m

Answer key

1. f_n = 15.92 Hz
2. f_n = 8.717 Hz
3. ζ = 0.1019
4. ζ = 0.02981
5. f_n = 1.482 Hz
6. k_eq = 70 kN/m

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