SME
College · Engineering
Mechanical Vibrations
4 topics
Mechanical
Before this course
Topics
Free vibration
Main lesson
Natural frequency from static deflection
Use this for “A 50 kg machine sags 2 mm on its mounts. Find the mount stiffness, ωₙ and fₙ.”
Springs in series and in parallel
Use this for “Springs of 3000 and 6000 N/m hold a 5 kg block. Find keq and ωₙ with the springs in parallel, then in series.”
A compound pendulum: a rod swinging from its end
Use this for “A uniform 2 kg rod 1 m long swings from a pin at one end. Find IO, ωₙ, fₙ and the period of small swings.”
Forced vibration and resonance
Main lesson
Transmissibility: how much force a mount lets through
Use this for “A pump runs at 3 times the natural frequency of its mount, with ζ = 0.05. What share of its shaking force reaches the floor?”
Rotating unbalance: the shaking of an off-balance rotor
Use this for “A 50 kg motor on 20,000 N/m mounts with ζ = 0.1 has a 0.01 kg·m unbalance and runs at 40 rad/s. Find the steady amplitude.”
Damping
Multi-degree-of-freedom systems
Main lesson
Tuned vibration absorber
Use this for “A pump runs at 1,500 rpm (157.08 rad/s) and shakes with a 150 N force. Size the spring for a 3 kg absorber, and find how far the absorber swings.”
Two masses on one spring, free at both ends
Use this for “A 5 kg glider and a 2 kg glider on an air track are joined by a 400 N/m spring. Find the frequency they vibrate at and the mode shape.”
Course test
See what you know: 10 questions on this course
New questions each time. Pass to mark it complete.