Global Positioning System (GPS) satellites circle Earth at altitudes of approximately \(20,000 \mathrm{km},\) where the gravitational acceleration has \(5.8 \%\) of its surface value. To the nearest hour, what's the orbital period of the GPS satellites?

Short Answer

Expert verified
The orbital period of the GPS satellites, rounded to the nearest hour, is 4 hours.

Step by step solution

01

Compute the radius of the orbit

Start by calculating the actual radius of the orbit, which is the Earth's radius plus the altitude of the GPS satellite. Using the Earth's radius as approximately \(6371 \mathrm{km}\) and the altitude \(20000 \mathrm{km}\), the orbital radius \(R = 26371 \mathrm{km} = 2.6371 \times 10^{7} \mathrm{m}\).
02

Identify the centripetal acceleration

In the problem it was stated that the gravitational acceleration at the altitude of the GPS satellites has \(5.8 \%\) of its surface value. So, the centripetal acceleration \(a\) is \(5.8\%\) of \(9.8 \mathrm{m/s^2}\), which gives us \(a = 0.058 * 9.8 \mathrm{m/s^2}\) rounding up to \(a = 0.569 \mathrm{m/s^2}\).
03

Apply the equation for centripetal acceleration

The formula for centripetal acceleration is \(a = \frac{v^2}{R}\), where \(v\) is the velocity and \(R\) is the radius. We can rearrange this to solve for \(v = \sqrt{aR}\). Substituting the values of \(a\) and \(R\) found earlier to find the velocity, \(v = \sqrt{(0.569 \mathrm{m/s^2})(2.6371 \times 10^{7} \mathrm{m})} = 3445.51 \mathrm{m/s}\).
04

Compute the orbital period using the found velocity

Now that we have the velocity, we can calculate the time it takes for the GPS satellite to complete one orbit. That is the orbital period \(T\). The formula for the period is \(T = \frac{2\pi R}{v}\). Substituting our values for \(R\) and \(v\), we find that \(T = \frac{2\pi (2.6371 \times 10^{7} \mathrm{m})}{3445.51 \mathrm{m/s}}\). After calculating this, the orbital period is roughly \(15251 \mathrm{s}\) or about \(4.23 \mathrm{hours}\). Rounding this to the closest hour, we get \(4 \mathrm{hours}\).

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