Mechanical waves require a medium to travel through and do not transport the medium itself. Examples of mechanical waves include sound waves, ocean waves, and seismic waves. Mechanical waves on a string can be visualized by focusing on a single point on the string. As a pulse passes through the point, it first displaces the point upwards by pulling on it, reaches a maximum upward displacement, then displaces it downward as the pulse continues through. The point returns to its original position once the pulse passes.

1. !
Mechanical waves travel through
a medium such as air, water or earth
Once the pulse has passes, the point is in the exact same
spot.This demonstrates an important concept in wave
mechanics: waves do not transport the medium
In contrast, electromechanical waves (such as light
waves) do not require a medium, but CAN travel through one
Sound waves
Ocean waves
Seismic Waves
Motion of a wave on a string
We’ll focus on a single point on
the string. It is currently not
accelerating, as Fnet = 0
A pulse approaches
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YOU
CAN
GO
YOUR
OWN
WAVE
As the pulse reaches the point, it
begins to pull the point upwards,
the point begins to move upwards,
but is still being pulled downwards
This continues until the point
comes to the highest point. Here,
it is being pulled downward by
both sides and has its maximum
acceleration
The point is moved downward
but is still pulled upward by the
leaving wave
MECHANICALWAVES AND THEIR TRAVEL
Mechanical wave motion can be very complex. A good simplification is a wave on a string
Then what DO waves do?
Waves transport ENERGY
Here’s what a
displacement vs. time graph
of this point looks like
Time
Displacement
Position - maximum
Velocity - 0
Acceleration - maximum and
opposing displacement
Mechanical waves can be
LONGITUDINAL particles move
parallel to wave (e.g. sound)
Mechanical waves can be
TRANSVERSE: particles move
at a 90 angle to wave