Problem

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The equation $y=-14 \cos (5 t)$ represents the motion of a weight hanging on a spring from the ceiling after it has been stretched 14 inches and released (ignoring air resistance and friction). The outpur, $y$, gives the position of the weight in inches (in) above (positive values of $y$ ) or below (negative values of $y$ ) the equilibrium point after $t$ seconds (s). Find the first four positive times when the weight is 4.7 inches below the equilibrium.

Note: make sure to put them in order! $t_{1}$ should be the first time the mass reaches equilibrium.
\[
\begin{array}{l}
t_{1}= \\
t_{2}= \\
t_{3}= \\
t_{4}= \\
\end{array}
\]

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Answer

\[\boxed{t_{1}= 34.94, t_{2}= 38.71, t_{3}= 42.48, t_{4}= 46.25}\]

Steps

Step 1 :The question is asking for the times when the weight is 4.7 inches below the equilibrium. This means we are looking for the values of \(t\) when \(y = -4.7\). So we need to solve the equation \(-14 \cos (5 t) = -4.7\) for \(t\).

Step 2 :We can start by isolating \(\cos (5 t)\) on one side of the equation. Then we can use the inverse cosine function to solve for \(5t\). Finally, we can divide by 5 to solve for \(t\).

Step 3 :Since the cosine function is periodic with period \(2\pi\), there will be infinitely many solutions. However, we only need the first four positive solutions.

Step 4 :The first four positive times when the weight is 4.7 inches below the equilibrium are approximately 34.94 seconds, 38.71 seconds, 42.48 seconds, and 46.25 seconds.

Step 5 :\[\boxed{t_{1}= 34.94, t_{2}= 38.71, t_{3}= 42.48, t_{4}= 46.25}\]

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