## Position Vector Following Changes of Course

The position vector of a body starting from a pointatwith constant velocityat any timeisIf the body makes a change of course at any timethe position vector will not be given by this expression. We must take account of the change of course by finding the position vector at the instant when the course change takes place and using this as the new starting pointWe must also take account of the fact that we are not now starting from this point atIf the change of course takes place atand the new velocity vector is the new position vector foris given byIf several changes of course occur we must apply this procedure at each change of course and the expression for the position vector will only be valid until the next course change.

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