Velocity is a vector in Newtonian mechanics

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Velocity can be defined as a vector in Newtonian mechanics using the principles of vector analysis outlined in Arfken and Weber's textbook. The transformation of a position vector under rotated coordinate axes demonstrates that its time derivative, representing velocity, also transforms in the same manner. This indicates that velocity adheres to the vector transformation rules, confirming its vector nature. The mathematical method employed, including tensor analysis, effectively supports this conclusion. Thus, the argument for velocity being a vector in Newtonian mechanics is validated through these transformations.
BookWei
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I studied the vector analysis in Arfken and Weber's textbook : Mathematical Methods for Physicists 5th edition.
In this book they give the definition of vectors in N dimensions as the following:
The set of ##N## quantities ##V_{j}## is said to be the components of an N-dimensional vector ##V##
if and only if their values relative to the rotated coordinate axes are given by
$$V_{i}^{'}=\sum_{j=1}^N a_{ij}V_{j},\;i=1,2,...,N$$
From the definition of ##a_{ij}## as the cosine of the angle between the positive ##x_{i}^{'}## direction
and the positive ##x_{j}## direction we may write (Cartesian coordinates)
$$a_{ij}=\frac {\partial x_{i}^{'}} {\partial x_{j}}$$

Can we use the same mathematical method (or tensor analysis) to prove the velocity is a vector in
Newtonian mechanics?
Many thanks!
 
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BookWei said:
Can we use the same mathematical method (or tensor analysis) to prove the velocity is a vector in
Newtonian mechanics?
Why not? If you have a position vector ##\vec X## that transforms according to ##X_{i}^{'}=\sum^3_{j=1} a_{ij}X_{j}##, then when you take the time derivative, ##\dot{X}_{i}^{'}=\sum_{j=1}^3 a_{ij}\dot{X}_{j}##. This says that ##\dot{\vec X}## transforms as a vector.
 

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