Section 2: Physics of Ultrasound

The Speed of Sound
Hooke's Law, when used along with Newton's Second Law, can explain a few
things about the speed of sound. The speed of sound within a material is a
function of the properties of the material and is independent of the amplitude
of the sound wave. Newton's Second Law says that the force applied to a
particle will be balanced by the particle's mass and the acceleration of the
particle. Mathematically, Newton's Second Law is written as F = ma. Hooke's
Law then says that this force will be balanced by a force in the opposite
direction that is dependent on the amount of displacement and the spring
constant (F = -kx). Therefore, since the applied force and the restoring force
are equal, ma = -kx can be written. The negative sign indicates that the force
is in the opposite direction.
F= ma = -kx