Hi I just have a quick question about Kinetic Energy. If we imagine an asteroid in empty space with no gravity field acting on it, i.e. it's just in empty space moving along according to Newtons 1st Law i.e. with constant velocity. Imagine a ship extends a magical robotic hand and exerts a force on the asteroid for a few seconds before letting it go, I want to know what happens. I would say that because K_2 - K_1 = ½mv² - ½mv_0² = Fd the asteroid will have a higher kinetic energy at the end when the robotic arm lets go. 1: But, say an hour later, the asteroid will still be moving forward, will it still have the same kinetic energy as it did when it was released from the robotic arm? No force is acting on it so no work is done but does the asteroid still have kinetic energy? 2: Also, if I use the kinetic energy as the asteroid is moving, well after it has been released, I will get the answer that the ship has no kinetic energy, what is wrong here? Does something have kinetic energy only while a force acts on it? I know it will have momentum as it moves but what about kinetic energy?