# What is relative velocity?

1. Dec 20, 2004

### DeathKnight

What is relative velocity? I have solved alot of questions relating to it but I'm still confused what EXACTLY is it? Its in my maths book so my mathematics teacher was not able describe this in detail. One more thing: I'll be much pleased if someone also explains what is relative path.
Thanks in advance for any help.
Abdullah.

Last edited: Dec 20, 2004
2. Dec 21, 2004

### dextercioby

I don't know what "relative velocity",which is a physics concept,has to do with math books,but i'll try to give an explanation.
Velocity is defined as the varition of coordinate wrt to time.Coordinate is defined wrt to a reference system which is composed by a point in space (considered fix) and a system of coordinate axis.In a 3D space,there are 3 independent axis,which are usually chosen as the Ox,Oy and Oz axis.Suppose that this reference system is labeled with "1".That is,a point (a body) wrt to this reference system has the coordinate:$x_{1}(t)$.I chosed it unidimensional for the simplicity of the exposure.Chose another reference system.Another point and another coordinate.Label it with "2".Then the same body has in this reference system the coordinate $x_{2}(t)$.The velocities for the 2 systems are $v_{1}(t)$ and $v_{2}(t)$.Assume that one reference system is fix (the one with the label "1") and the one with the label "2" is moving with the speed $v$ wrt to the system "1" which,as i said,i assumed fix.Then the RELATIVE VELOCITY OF THE BODY wrt to the moving frame is
$$v_{2}=v_{1}-v$$

The concept of relative velocity appears whenever you're dealing with more than one reference system.U must know that the concept of "velocity" requires a reference system.When there's one moving body,but more reference systems,then u can define the "relative velocity".

Daniel.

3. Dec 21, 2004

### DeathKnight

I feel the same way man. Its not actually in my maths book its in my addition Mathematics book(o'levels). They even had particle machanics in it with work energy power. I had the option to choose biology or Additional mathematics and I chose Additional Maths.
By the way thats for replying.

Last edited: Dec 21, 2004
4. Dec 21, 2004

### bionic_atom

At dictionary.com
Relative Velocity - the velocity with which a body approaches or recedes from another body, whether both are moving or only one.

If this is not clear try looking it up in an advance physics glossary.