Universal Gravitation?

Question

I don't even understand these questions, I have for homework.
1)Many people mistakenly believe that the astronauts who orbit the earth are "above gravity." Calculate g for space shuttle territory, 245 kilometers above the earth's surface (dashed line in sketch). Earth's mass is 6x10^24 kg, and its radius is 6.38x10^6 m (6380 km). (b) Your answer is what percentage of 9.8 m/s2?
2)The intensity of light from a central source varies inversely as the square of the distance. If you lived on a planet only half as far from the sun as our earth, how would the light intensity compare with that on earth? How about a planet ten times as far away as the earth?

Answer 1

1. The force of gravity is inversely proportional to the square of the distance between the centers of gravity of things. Since the radius of the Earth is 6380km, that is the distance between the center of gravity of the earth and any object on the surface of the Earth. Objects at the altitude of the space shuttle are 245 km farther away from the center of the Earth.
gSpaceShuttle/gSurface=6380^2/6625^2
gSpaceShuttle=6380^2/6625^2*gSurface
gSpaceShuttle=0.92740534*9.8=9.088572332

2.a. An inverse relationship means that when one thing gets bigger the other gets smaller. distE^2/distP^2=brightP/brightE
distE/distP=2
distE^2/distP^2=4
brightP=4*brightE

2.b. distE/distP=.1
distE^2/distP^2=.01
brightP=.01*brightE