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Preparatory Notes for ASNT NDT Level III Examination - Ultrasonic Testing, UT

Preparatory Notes for ASNT NDT Level III Examination - Ultrasonic Testing

Preparatory Notes for ASNT NDT Level III Examination - Ultrasonic Testing

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4.0 The Speed of Sound<br />

Hooke's Law, when used along with Newton's Second Law, can explain a few<br />

things about the speed of sound. The speed of sound within a material is a<br />

function of the properties of the material and is independent of the amplitude<br />

of the sound wave. Newton's Second Law says that the <strong>for</strong>ce applied to a<br />

particle will be balanced by the particle's mass and the acceleration of the the<br />

particle. Mathematically, Newton's Second Law is written as F = ma. Hooke's<br />

Law then says that this <strong>for</strong>ce will be balanced by a <strong>for</strong>ce in the opposite<br />

direction that is dependent on the amount of displacement and the spring<br />

constant (F = -kx). There<strong>for</strong>e, since the applied <strong>for</strong>ce and the restoring <strong>for</strong>ce<br />

are equal, ma = -kx can be written. The negative sign indicates that the <strong>for</strong>ce<br />

is in the opposite direction.<br />

F= ma = -kx

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