3.5 Relative Velocity
You’ve no doubt observed how a car that is moving slowly forward appears to
be moving backward when you pass it. In general, when two observers measure the velocity of a moving body, they get different results if one observer is
moving relative to the other. The velocity seen by a particular observer is
called the velocity relative to that observer, or simply relative velocity. Figure
3.31 shows a situation in which understanding relative velocity is extremely
important.