If we throw a stone at an angle to the horizontal, it follows a parabolic path. Another second stone is also thrown with the same speed and at the same angle alongside the first. An insect sitting on the second stone who have some idea of Mechanics, observes the path of first stone and decares that it does not have any kinetic energy at all. Who is right, you or the insect ?How does the law of conservation of energy fit into this situation (with respect to you and insect) ?