http://www.ck12.org Chapter 10. Periodic Motion
FIGURE 10.12
A wave from the 2004 Boxing Day
tsunami crashing through palm trees in
Thailand.FIGURE 10.13
The aftermath of a tsunami.Longitudinal waves
Alongitudinal waveconsists of vibrations that are parallel to the wave direction. Examples include sound, or an
earthquake P-wave. Such a wave is generated by pressing back and forth in the direction that the wave goes. How
does a longitudinal wave transport (or propagate) energy?
Imagine a long coiled spring stretched out several meters in length. If several coils of the spring are compressed and
then released, you will see a pulse move through the spring as inFigure10.14. If coils are continually compressed
and released, a train of compressions and expansions (a set of vibrations, or a wave) will appear to move through
the spring. The energy propagating through the spring results in the vibrations of the spring coils. The vibrations
cause the coils of the spring to oscillate about their equilibrium positions. It is important to realize that there is no
net transfer of mass through the spring. Only energy is transferred. The properties of the spring such as its mass,
tension, and force constant will determine at what speed the energy is propagated.