According to Alice's frame of reference, there is a 1kg object moving through space at 1 m/s along the x coordinate. When x = 0 meters, Alice applies 1 Newton of force to the object in the positive x direction. However, Bob simultaneously applies 1 Newton of force in the opposite direction. When the object is at x = 1 meter, and Alice and Bob have each applied 1 Newton to the object (in opposite directions), Alice notes that the object moved 1 meter along the direction that she applied her force of 1 Newton. According to the definition of Work, Work = Force * distance moved in the direction of the force. W = 1N * 1m, which means she transferred 1 Joule of energy to the object. Yet Alice is perplexed that she sees no evidence of the object's increased energy. When told that Bob was also applying 1 Newton of force to the object, but in the opposite direction, Alice says "I am not the object's keeper. As far as I know, there are a billion forces acting on that object in every different direction. All I know is that I applied 1 Newton of force to an object that moved 1 meter in the direction of my force, and fulfilled the requirements of the definition of work." When told that the object was moving in her frame prior to her application of her force, Alice says "The object's energy - including its kinetic energy - prior to my interaction with it is none of my business. If that object was full of gasoline instead of water, I would have increased its energy by just as much with my interaction. I only know how much force I applied to it in the direction that it moved." Is Alice wrong, and if so why? I have a feeling she is, but I would like it to be explained in the context of work as a relativistic concept (relative of frame and velocity) Note: This is not a homework question.