| __Celestial Mechanics__ *(Site not responding. Last check: 2007-11-05)* |

| | **Vector** subtraction is defined by A - B = A + (-B), where the **vector** -B has the same magnitude as B but the opposition direction. |

| | Forces can be added just like **vectors**, so that force 1 and force 2 add together to produce the total force, F. Total force F can also be broken into components x and y that correspond to the forces in the x and y directions (for example, along a road and with gravity). |

| | With **vector** calculus, Newton was able to develop a cosmology which included the underlying cause of planetary motion, gravity, completed the solar system model begun by the Babylonians and early Greeks. |

| zebu.uoregon.edu /~js/ast221/lectures/lec08.html (1038 words) |