Ok I have an answer for this but my method is so simple is must be wrong. Question The work done against a firce F(r) in moving an object from r=r1 to r=r2 is integralF(r) dr limits R2 at top and r1 at bottom. The gravitational attraction between two masses m1 and m2 at distance d is given be F=GMM/d^2, G=6.67*10^-11. Find the work done in lifting a 4000kg payload from the surface on the moon to a height of 25000m above its surface. The mass of the moon can be taken as 7.3*10^22 and its radius at 1.7*10^6. My answer. I subbed in the values for F getting 6739.24 then integrated with respect to r within the limits of 25000 and 0 and got an answer of 1.68*10^8j! What am i doing wrong???