Another question!! Gravitaional Force ? I know this is easy, but for some reason I am getting stuck! The mass of a robot is 5450kg. This robot weighs 3620N more on Planet A than on Planet B. Both planets have a radius of 1.33^7. What is the difference Ma-Mb in the masses of these planets. I think that I need to set the gravitaional force on A(minus 3620) equal to gravitaional force on B. I know teh G and the r's are the same. I am confused on how to put it into the formula and figure out what I am looking for?