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**1. The problem statement, all variables and given/known data**

A) Suppose you are on Earth's equator and observe a satellite passing directly overhead and moving from west to east in the sky. Exactly 12.0 hours later, you again observe this satellite to be directly overhead. How far above the earth's surface is the satellite's orbit?

B) You observe another satellite directly overhead and traveling east to west. This satellite is again overhead in 12.0 hours. How far is this satellite's orbit above the surface of the earth?

A) Suppose you are on Earth's equator and observe a satellite passing directly overhead and moving from west to east in the sky. Exactly 12.0 hours later, you again observe this satellite to be directly overhead. How far above the earth's surface is the satellite's orbit?

B) You observe another satellite directly overhead and traveling east to west. This satellite is again overhead in 12.0 hours. How far is this satellite's orbit above the surface of the earth?

**2. Relevant equations**

T=(2πr^3/2)/(√Gm)

**3. The attempt at a solution**

Well, I thought that they would both have the same altitude since they have the same period. This is evidently not correct since the back of the book has two different answers for A and B.

I plugged in the numbers for the variables. I dropped the units. I would have looked very messy.

86400=(2πr^3/2)/(√(6.67x10^-11)(5.97x10^24))

I solved for r

r=42226910.15m

altitude= r-Re=35846910.18m which matched what the book has as an answer for B, but why is this the answer for B. Why would they both have different altitude if they have the same period, but in opposite direction? May I get any hint for part A and some clarification on part B?