Resonance occurs when an object is driven at its natural frequency, causing oscillations to build up rapidly. There are three conditions for resonance: 1) an object with a natural frequency, 2) a forcing function at the same frequency, and 3) a lack of damping. When these conditions are met, the oscillations reinforce each other and grow larger. Examples of resonance include playground swings, washing machines, opera singers shattering wine glasses, and bridges collapsing from marching soldiers.

1. RESONANCE

2. WHAT IS RESONANCE
 When an object is driven at its natural frequency so that it
oscillates with a large amplitude.
 In resonance the oscillation occurs at a specific frequency.
These oscillations build up rapidly to very high levels.
Ultimately some of the energy in the oscillations has to be
removed from the object or the size of the oscillations get so
large that the object breaks.
 Without resonance we wouldn't have radio, television, music,
or swings on playgrounds, not to mention cool gismos like
Tesla coils.
 resonance also has its dark side. It occasionally causes a
bridge to collapse, a helicopter to fly apart, or other
inconveniences

4. RESONANCE REQUIRES 3 BASIC CONDITIONS:
 A) An Object With a Natural Frequency: The object can be a
mechanical device or an electronic circuit. An object's natural
frequency is the frequency it tends to oscillate at when
disturbed. The oscillation can be a mechanical vibration as is
the case when the string of a guitar is strummed. In an
electronic circuit the oscillation is a variable voltage or
current. An object can have more than one natural frequency.
These are called harmonics. A guitar string sounds musical
because it vibrates with several harmonics when it is
strummed.

5. RESONANCE REQUIRES 3 BASIC CONDITIONS:
 B) A Forcing Function at the Same Frequency as the Natural
Frequency: In mechanical systems the forcing function is a
variable force. In electronic circuits it arises from a variable
electric field. In either case the forcing function does work on
the object it is applied to. Since work is a form of energy
transfer it causes energy to build up in the object.

6. RESONANCE REQUIRES 3 BASIC CONDITIONS:
 C) A Lack of Damping or Energy Loss: For an object to
resonate, mechanical or electrical energy has to build up in
the object. Anything which removes these forms of energy
tends to interfere with resonance. Damping is a means
of removing electrical or mechanical energy by converting it
to heat. The term damping should not be confused with the
term dampening which means to make something slightly
wet. Friction, air resistance, and viscous drag can all provide
damping in mechanical systems. Electrical resistance
performs the same function in electronic circuits. Other forms
of energy loss can include sound (musical instruments) or
light emissions (lasers).

7. HOW IT WORKS?
 When the forcing function's
frequency matches the natural frequency of
an object it will begin to resonate. The
forcing function adds energy at just the
right moment during the oscillation cycle
so that the oscillation is reinforced. This
makes the oscillation's amplitude grow
larger and larger. These oscillations would
eventually become infinitely large.
However, as mentioned earlier, long before
the oscillations reach infinity one of three
things happens: 1) the object's dynamics
change so that the resonant frequency and
forcing functions no longer match, 2) the
energy lost as heat, sound, or light becomes
equal to the energy input. or 3) the object
breaks

8. HOW IT WORKS?

9. EXAMPLES: PLAYGROUND SWINGS
 The natural frequency of the swing is not influenced by the mass of the
person in it. In other words' it makes no difference whether a swing has a
large adult or a small child in it. It will have the about the same natural
frequency. Slight differences can be caused by slightly different locations
of the person's center of mass. This is located about two inches below the
navel. When people are sitting the center of mass is in about the same
place relative to the seat of the swing regardless of whether the person is
an adult or a child.
 If a forcing function is applied to a swing at the natural frequency of the
swing it will resonate. The amplitude of the swing will increase during
each back and forth cycle. The forcing function can be provided by a
second person pushing on the swing. In this case even a small child can
make a large adult swing by pushing in sync with the swing's back and
forth cycle. The forcing function can also be provided by the person in
the swing. In this case the person in the swing shifts her center of mass
very slightly by changing the position of her legs or torso. This creates a
slight pushing force which makes the swing go higher and higher. It
takes a very small force but it has to be timed perfectly.

10. EXAMPLES: PLAYGROUND SWINGS
 The big question is what keeps the swing from flying apart or
spinning over the top of the swing's frame and subsequently killing
its rider? After all, if it is a resonating system then it should be very
dangerous to keep applying force in time with the swing's
frequency. The answer is fairly simple. The equation given above is
only good for small angles. When the swing goes beyond a certain
height it is no longer possible for the person in it to apply the
necessary small force in sync with the natural frequency because the
natural frequency changes. In other words the motion of the system
is naturally limited.

11. EXAMPLES: PLAYGROUND SWINGS

12. EXAMPLE: WASHING MACHINE
 By far the most common problem for a washing machine that
is shaking or is vibrated is that the load inside of it is uneven
or unbalanced. It is often necessary to make sure that enough
clothing is placed around the entire basin. If too much
clothing is on one side as opposed to the amount on the
other, this can cause the load to be off balance during the spin
cycle. This will cause it to jump from side to side in drastic
differences or vibrate and shake when there is just a bit too
much on one side or the other.
 The washer also needs to be sitting on a level surface is it will
be steady during the washing process. The washer should be
sitting on a level surface and that surface has to be strong
enough to support the heavy wait of the water inside the
unit.

13. EXAMPLE: OPERA SINGER
 Opera singers can shatter a wineglass by singing a note that is
exactly the same as the glass's resonant frequency. When the
singer sings the note, the glass begins to vibrate and "sing" the
same note itself. If the singer holds the note for several
seconds, the vibrations become extremely powerful, shaking
the glass until it smashes.

14. BREAKING A WINE GLASS USING RESONANCE

15. EXAMPLE: BRIDGE
 a group of soldiers marching across a bridge can cause it to
crumble, even though it is capable of holding much more than
their weight, if the rhythm of their synchronized footsteps
resonates with the natural frequency of the bridge. For this
reason, officers or sergeants typically order their troops to do
something very unmilitary—to march out of step—when
crossing a bridge.

17. COLOR FOOTAGE OF TACOMA NARROWS

18. BIBLIOGRAPHY
 http://www.intuitor.com/resonance/index.php
 http://www.appliancejournal.com/appliance-repair-
help/washing-machine-repair-why-is-my-washing-machine-
shaking-113/
 http://www.infoplease.com/dk/science/encyclopedia/musi
cal-sound.html
 http://www.answers.com/topic/resonance