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
Clarke's three laws same time. Clarke's first law was proposed in the 1962 edition of the essay, as "Clarke's Law" in "Profiles of the Future". The second law is offered as a simple observation in the same essay but its status as Clarke's second law was conferred by others. It was initially a derivative of the first law and formally became Clarke's second law where the author proposed the third law in the 1973 revision of "Profiles of the Future," which included an acknowledgement"." It was also here that Clarke wrote about the third law in these words: "As three laws were good