1. The problem statement, all variables and given/known data An object of mass m is moved straight up by a distance h. The work that gravity does on the object is: (a) -mh (b) +mh (c) -mgh (d) +mgh (e) None of the Above 2. Relevant equations Work = ∫F dl PE = mgh 3. The attempt at a solution I have a feeling the answer is (c) -mgh because work is done to lift the object. The object is gaining potential energy so it's gaining +mgh and due to Newton's 3rd law, the work done by gravity is -mgh. Is that right?