#### willbland

1. Homework Statement

The polar-orbiting environmental satellites (POES) and some military satallites orbit at a much lower level in order to obtain more detailed information. POES complete an earth orbit 14.1 times per day. What are the orbital speed and the altitude of POES?

T = 1.7 h
G = 6.67x10^-11
M earth = 5.98x10 ^24

2. Homework Equations

The international space station orbits at an altitude of approximately 226km. What is its orbital speed and period?

3. The Attempt at a Solution

What i tried to do was,

R^3 = (G)(M Earth)
T^2 _____4π^2

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#### D H

Staff Emeritus
T = 1.7 h
G = 6.67x10^-11
M earth = 5.98x10 ^24
You have units for the orbital period, why not for G and the mass of the Earth? Those things have units too, and unless you apply them consistently you will get the wrong answer. You used the values $G=6.67*10^{-11}\mathrm{m}^3/\mathrm{kg}/\mathrm{s}^2$ and $M_{\oplus}=5.98*10^{24} \mathrm{kg}$ in conjunction with time in hours and distance in kilometers.

#### willbland

Thank's.

So how do i do the question?

#### D H

Staff Emeritus
Make sure you use consistent units throughout. That value of G is in m3/kg/s2. If you want to use that particular value, you had better represent lengths in meters, not kilometers, and time in seconds, not hours.

#### willbland

Ooo.. Thanks man :)

But how do i use the equasion when they only give that much information, i am lost :( But i do understand your point.

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