This image was copied from wikipedia:pt. The original description was:

Velocidade depende de um referencial. No diagrama de baixo, uma câmera posicionada sobre um trilho ao lado do objeto, viajando com a mesma velocidade (v₁ = v₂) não acusaria o movimento do objeto: ele parmeneceria como que "parado" em frente a ela, sendo registrado a todo instante.

Source code edit

Essa imagem foi gerada através de um código SVG, disponível a seguir:

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v
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1 
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câmera
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