A ball is thrown into the air with 100J of kinetic energy. When it returns to its original level after encountering air resistances what is it kinetic energy? I have KE = 0.5m * v^2 I am not sure how to approach this problem as I don't have the mass or the velocity or the height of the ball. am I using the wrong formula? once it starts falling down isn't it really gravitation potential energy? is there really any kinetic energy there once its heading downwards? doesn't kinetic energy depend on the frame of reference? I am not sure what the teacher wants here in this answer. I think I am not really understanding the question. help?