A buoy starts at a height of 0 in relation to sea level and then goes up. Its maximum displacement in either direction is 6 feet, and the time it takes to go from its highest point to its lowest point is 4 seconds.

Which of the following equations can be used to model [tex]\( h \)[/tex], the height in feet of the buoy in relation to sea level as a function of time, [tex]\( t \)[/tex], in seconds?

A. [tex]\( h = 4 \sin \left(\frac{\pi}{6} t\right) \)[/tex]
B. [tex]\( h = 4 \sin \left(\frac{\pi}{3} t\right) \)[/tex]
C. [tex]\( h = 6 \sin \left(\frac{\pi}{4} t\right) \)[/tex]
D. [tex]\( h = 6 \sin \left(\frac{\pi}{2} t\right) \)[/tex]



Answer :

To determine which of the given equations models the height, [tex]\( h \)[/tex], of the buoy in relation to sea level as a function of time, [tex]\( t \)[/tex], we need to consider the characteristics of the buoy's motion.

1. Amplitude:
The maximum displacement of the buoy from the sea level is 6 feet. Therefore, the amplitude, [tex]\( A \)[/tex], of the sinusoidal function should be 6. This means that in our equation, the coefficient in front of the sine function should be 6.

2. Period:
The buoy takes 4 seconds to go from its highest point to its lowest point. This is half of the period of the sine function (since a full cycle goes from highest point to lowest point and back to the highest point). Therefore, the full period [tex]\( T \)[/tex] of the function is 8 seconds.

3. Form of the equation:
The general form of the sinusoidal function is:
[tex]\[ h(t) = A \sin(B \cdot t) \][/tex]
where [tex]\( A \)[/tex] is the amplitude and [tex]\( B \)[/tex] is related to the period by:
[tex]\[ B = \frac{2\pi}{T} \][/tex]

4. Calculate [tex]\( B \)[/tex]:
Since the period [tex]\( T \)[/tex] is 8 seconds, we have:
[tex]\[ B = \frac{2\pi}{8} = \frac{\pi}{4} \][/tex]

So our equation should be:
[tex]\[ h(t) = 6 \sin\left(\frac{\pi}{4} t\right) \][/tex]

Now, let's compare this with the given options:

1. [tex]\( h = 4 \sin \left(\frac{\pi}{6} t\right) \)[/tex]
2. [tex]\( h = 4 \sin \left(\frac{\pi}{3} t\right) \)[/tex]
3. [tex]\( h = 6 \sin \left(\frac{\pi}{4} t\right) \)[/tex]
4. [tex]\( h = 6 \sin \left(\frac{\pi}{2} t\right) \)[/tex]

The correct equation that matches our parameters (amplitude 6 and [tex]\(B = \frac{\pi}{4}\)[/tex]) is:

[tex]\[ \boxed{3} \][/tex]

Hence, the equation [tex]\( h(t) = 6 \sin\left(\frac{\pi}{4} t\right) \)[/tex] correctly models the height of the buoy in terms of time.

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