I have a final project for physics on circular motion, gravitation and Kepler's Laws. I have a set of 7 questions I need to answer first, but I am stuck. 1.) Planet 1 orbits your star in 7.69 x 10 seconds. Find:

a.) The mass of your star

b.) Planet 1's mean orbital radius (In meters)

c.) Planet 1's velocity (m/s)

2.) Planet 1 has a Kepler Constant of 1.24 x 10. If the radius of Planet 1 is 8 x 10, find:

a.) Planet 's mass

b.) The acceleration due to gravity at a height of 2000km above the surface.

3.) A synchronous (stays above the same spot) satellite is placed in orbit above Planet 1. Planet 1 has a period of rotation about its axis of 8.85 x 10 seconds. How high above the surface must be the satellite placed?

4.) One of Planet 1's moons orbits Planet 1 at a speed of 1677 m/s. Find:

a.) The orbital radius of this moon

b.) The moon's distance away from Planet 1's surface.

c.) The time it takes the moon to orbit Planet 1, 5 times.

5.) Find the height above the surface of Planet 1 that a 100kg astronaut would weigh 4 times less than what he weighs on at Planet 1's surface.

6.) Planet 2 orbits your star once every 8.43 x 10 seconds. What is the orbital radius of Planet 2?

7.) A visiting astronaut to Planet 2 found he weighs the same as they did back on Earth. If Planet 2's radius is 5.82 x 10m, what is the mass of Planet 2.

Constant for Star: 5.72 x 10
Constant for Planet 1: 1.24 x 10
Moon Orbital Speed 1677 m/s

Any help would be appreciated, thanks.