1. The problem statement, all variables and given/known data Assume that the orbital radius of the earth decreases from R to R-ΔR due to air drag, provided the change is very small compared to the radius of earth. Then what is change in orbital velocity, change in kinetic energy, change in potential energy and work done by air resistance? 2. Relevant equations F = Gm1m2/r2 Kinetic energy = 1/2 mv2 Potential energy = mgh 3. The attempt at a solution Work done by air resistance is Gm1m2Δr/r2 ?