2.1. in the real world, g is 6.67x10-11 nm2/kg2. the programmer of this applet did not use this number. computers are much quicker at computing with integers than very small numbers like g. to control this program and calculate orbits, the number the program uses for g in the simulation will have to be measured. this can be done using newton's synthesis.
2.2. to solve newton's synthesis, start by setting the equation for net force acting in the centripetal direction equal to the force of gravity equation: σfc = fg . substitute the respective formulas and solve the equation for g. label one mass star and the other planet (it could also be planet with moons, or planet with satellites). for newton's synthesis, what is the equation for fg using g for the gravitational constant, ms for the mass of the sun (central object), mp for the mass of the planet, r for the radius or distance from sun (central object) and v for velocity of the planet?