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**[SOLVED] gravity fun**

**1. Homework Statement**

1. Calculate the speed of objects on the earth's surface caused by the earth's own rotation around its own axis.

2. Find the mass of the earth using its time period of revolution of the moon around the earth.

3. Find the mass of the sun using the time period of the earth around the sun.

4. What is the radius for a geo-synchronous satellite?

**2. Homework Equations**

The time period of revolution of the moon around the earth is 28 days?

**3. The Attempt at a Solution**

1. v= 2piR/T = 2pi (6.4E6) / (24hours*60min*60s) = 4.65E2

2. I know how to solve this using F = GmM/(R^2) = mg but I don't know how to use the given 28 days. The answer to this problem should be around 6E24 kg

3. The answer is around 2E31 kg

4.

Thanks in advance!

**1. Homework Statement**

**2. Homework Equations**

**3. The Attempt at a Solution**

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