You need to include:

an explanation of gravity
an explanation of how mass determines (or affects) the force of gravity
an explanation of the part air resistance plays
an example of the force of gravity (be creative)

The illuminance of a surface varies inversely with the square of its distance from the light source. if the illuminance of a surface is 120 lumens per square meter when its distance from a certain light source is 6 meters, by how many meters should the distance of the surface from the source be increased to reduce its illuminance to 30 lumens per square meter?