What is the net force on the object?

F(net) = Fgrav -Fair

         = 600 -400

         =200N

then net force is equal to 200N..

the earths atmosphere is made up of nitrogen and oxygen. solids can turn into gasses through a process called sublimation. sublimation is the transition of a substance directly from the solid to the gas phase, without passing through the intermediate liquid phase.

hope this : d