Vector Physics..... I can completely understand why the idea of vectors works for distances. ie - you can use pythagora and trig to work things out. However, why should that be the same when we are dealing with forces, velocity, etc? In other words, why if we represent forces as certain lengths should they obey Pythagoras' theorum? Please could someone proove why this works to me - maths in explanation is wellcome. Thanks in advance.