When pushing a child on a swing, you must give them a push periodically to keep them moving. this seems to go against the law of inertia and the conservation of energy. when pushing a child on a swing, you must give them a push periodically to keep them moving. this seems to go against the law of inertia and the conservation of energy. why does the child need a push periodically to keep moving. a) energy is lost over time slowing down the swing. b) all objects will naturally come to rest over time. c) a wind must have been blowing in the opposite direction. d) friction provides an outside force slowing the swing down.