how can we identify a vector quantity
Answers
A very simple rule of thumb is if someone asks you to calculate the quantity and you end up asking in which direction, the quantity is a vector.
I will provide a very simple analogy. Suppose you go the market and ask for 1kg of veggies, the shopkeeper wont ask you the direction of measurement. But suppose I ask you to apply say 5N force on a box (assuming you know how much is 5N force), you will immediately ask me in which direction to apply the force? Do you apply in the sides? Or the front face? Or some weird angle? All these will give different outcomes. So you can safely say in the first case, mass is scalar and second case, force is a vector.
Of course this is a very crude method. A more accurate will be a mathematical approach. You select a frame of reference. You measure the quantity. Then change the frame of reference by rotating or translating or both your original co-ordinate axes. If the quantity remain invariant, you have a scalar, or else you have a vector (a more general term would be a tensor).
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Explanation:
If a physical quantity has direction that it can act in is a vector quantity
Ex:- Mass exists but has no relation with direction which means mass is a scalar quantity but velocity depends on direction so its a vector quantity