Equations of motion modification consistent with conservation of momentum, see variable-mass system. It may be simple to write down the equations of motion in vector form using Newton's laws of motion, but the components may vary in complicated ways with spatial coordinates and time, and solving them is not easy. Often there is an excess of variables to solve for the problem completely, so Newton's laws are not always the most efficient way to determine the motion of a system. In simple cases of rectangular geometry, Newton's laws work fine in Cartesian coordinates, but in other coordinate systems can become dramatically complex. The
Three Laws of Robotics Three Laws. However, the 1960s German TV series "Raumpatrouille – Die phantastischen Abenteuer des Raumschiffes Orion" ("Space Patrol – the Fantastic Adventures of Space Ship Orion") bases episode three titled ""Hüter des Gesetzes"" ("Guardians of the Law") on Asimov's Three Laws without mentioning the source. References to the Three Laws have appeared in popular music ("Robot" from Hawkwind's 1979 album "PXR5"), cinema ("Repo Man", "Aliens", ""), cartoon series ("The Simpsons"), tabletop roleplaying games (Paranoia) and webcomics ("Piled Higher and Deeper" and "Freefall"). Robby the Robot in "Forbidden Planet" (1956) has a hierarchical command structure which keeps him from harming humans,