1. The problem statement, all variables and given/known data A bullet was shot at 40m/s Elevation angle : 37° Bullet mass = 0.01 Kg Question : how much work is done by the force of gravity to the bullet since it was shot until it reaches the ground again 2. Relevant equations mgh = E.Pot 1/2mv ^2 = E kinetic 3. The attempt at a solution My teacher said, Work = F.S =0 joule, because gravity is only pulling downwards in this case, but S (distance) is in X axis, which means if we use horizontal Force, it will be zero, thus the work is Zero. If we use the vertical distance, it is zero. Thus the work is zero in both case (Work in X and Y axis) Okay, i understand the logic in there. It suits the math But my REAL question, Certain amount energy was needed to shoot the bullet, correct? But somehow, the gravity make the suppossedly moving bullets back to stationary condition. Doesn't that require energy? To stop something moving? So how can the answer be 0 joule :/ I have said this to my teacher but she doesn't seem to give a satisfying logical answer. Can you help me? .,.