Slides in this set
What is natural frequency?
· When you hit an object it will vibrate, creating
· It will tend to vibrate at a single frequency or
set of frequencies.
· This frequency is known as that objects
· If the sound wave produced has a large
amplitude and a frequency within the range of
the human ear the sound will be audible…read more
· You can force an object to oscillate at any
· Forced vibrations happen when there is an
periodic external driving force.
· The frequency of this is called the driving
frequency. If this is equal to the natural frequency
the amplitude will grow. This is RESONANCE.
· Resonance can be dangerous and destructive, if
the amplitude grows too much glass etc. can
· Damping occurs when energy is lost to its
surroundings. It absorbs energy and reduces the
effect of resonance
· Damping forces include frictional forces like air
· Systems can be deliberately dampened to stop
oscillation and minimize the effects of resonance.
· It is often used to earthquake proof buildings.
· As damping increases: Amplitude decreases and
the resonant frequency gets lower.…read more
Tacoma Narrows Bridge
· In 1940 in Tacoma, WA, USA, the Tacoma Narrows
suspension bridge collapsed 3months after its
· A steady cross wind created swirling air causing
the bridge to vibrate. Unfortunately these
vibration matched the natural frequency.
· Although many measures were taken, the bridge
continued to resonate and oscillate more and
more violently eventually becoming too much for
the structure, causing the bridge to collapse.…read more
Tacoma bridge continued
· This event is well known among bridge engineers
and has allowed further technology in bridge
dampening to be developed.
· Other bridge disasters include 200 french soldiers
died as they were marching across a bridge,
collapsing it due to their marching over resonating.
Soldiers now have to break march when crossing a