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

An 80 kg mass hangs from a spring with a stiffness of 80 kN/m. Ignore damping. Find the natural circular frequency ω_n in rad/s.

m = 80 kgk = 80 kN/m

ω_n = rad/s

2.Easy

A 200 kg mass hangs from a spring with a stiffness of 100 kN/m. Ignore damping. Find the natural frequency f_n in Hz.

m = 200 kgk = 100 kN/m

f_n = Hz

3.Medium

A 200 kg mass on a spring with a stiffness of 20 kN/m has a viscous damper giving a damping ratio of 0.7. Find the damped natural frequency f_d of its free vibration in Hz.

m = 200 kgk = 20 kN/mζ = 0.7

f_d = Hz

4.Medium

A 20 kg mass is supported by a spring with a stiffness of 20 kN/m and a viscous damper with a damping coefficient of 760 N·s/m. Find the damping ratio ζ.

m = 20 kgk = 20 kN/mc = 760 N·s/m

ζ =

5.Hard

A 25 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 = 40 kN/m. Find the equivalent stiffness k_eq of the spring system in kN/m.

m = 25 kgk₁ = 20 kN/mk₂ = 40 kN/m

k_eq = kN/m

6.Hard

A 10 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 = 25 kN/m. Find the equivalent stiffness k_eq of the spring system in kN/m.

m = 10 kgk₁ = 100 kN/mk₂ = 25 kN/m

k_eq = kN/m

Answer key

1. ω_n = 31.62 rad/s
2. f_n = 3.559 Hz
3. f_d = 1.137 Hz
4. ζ = 0.6008
5. k_eq = 13.33 kN/m
6. k_eq = 20 kN/m

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