Trigonometry (10th Edition)

Published by Pearson
ISBN 10: 0321671775
ISBN 13: 978-0-32167-177-6

Chapter 4 - Graphs of the Circular Functions - Section 4.5 Harmonic Motion - 4.5 Exercises - Page 180: 19a

Answer

$s(t)=-3\cos 12t$

Work Step by Step

The general equation regarding the oscillation of a weight attached to a spring is $s(t)=a\cos wt$. Since the weight is first pulled down and then released, the equation becomes $s(t)=-a\cos wt$. Also, as the weight is pulled down 3 inches, the amplitude of the motion is 3. The equation therefore becomes $s(t)=-3\cos wt$. Now we need to find $w$. Since the frequency is $\frac{6}{\pi}$, the period is $\frac{\pi}{6}$ since the two are reciprocals of each other. Now, we can use the following formula to find $w$: Period$=\frac{2\pi}{w}$ $\pi/6=\frac{2\pi}{w}$ $w=\frac{2\pi}{\pi/6}$ $w=12$ Therefore, the model that gives the position of the weight at time $t$ is $s(t)=-3\cos 12t$.
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