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

m = 40 kgk = 10 kN/m

ω_n = rad/s

2.Easy

A 25 kg mass hangs from a spring with a stiffness of 5 kN/m. Ignore damping. Find the natural frequency f_n in Hz.

m = 25 kgk = 5 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 one cycle later by a peak of 11 mm. Find the damping ratio ζ.

x₀ = 15 mmx₁ = 11 mmn = 1

ζ =

4.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 =

5.Hard

A 50 kg mass hangs from two springs connected end to end (in series): the upper spring has k₁ = 100 kN/m and the lower one k₂ = 10 kN/m. Ignore damping and the masses of the springs. Find the natural frequency f_n of vertical vibration in Hz.

m = 50 kgk₁ = 100 kN/mk₂ = 10 kN/m

f_n = Hz

6.Hard

A 40 kg mass hangs from two springs connected end to end (in series): the upper spring has k₁ = 10 kN/m and the lower one k₂ = 30 kN/m. Find the equivalent stiffness k_eq of the spring system in kN/m.

m = 40 kgk₁ = 10 kN/mk₂ = 30 kN/m

k_eq = kN/m

Answer key

1. ω_n = 15.81 rad/s
2. f_n = 2.251 Hz
3. ζ = 0.0493
4. ζ = 0.1019
5. f_n = 2.146 Hz
6. k_eq = 7.5 kN/m

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