What is a scalar quantity and a vector quantity?                                        

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A scalar quantity is one which is described by its magnitude. It has no direction or it does not require a direction for its complete description. The speed of a body is an example of a scalar quantity. That is why we always mention that the speed of an object...

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A scalar quantity is one which is described by its magnitude. It has no direction or it does not require a direction for its complete description. The speed of a body is an example of a scalar quantity. That is why we always mention that the speed of an object is, for example, 30 m/s (magnitude). One can also think of a scalar quantity as having a one-dimensional description or measurement.

A vector quantity, in comparison, requires both magnitude and direction for its complete description. Velocity is an example of a vector quantity. Thus, we need to say "velocity of a body going north (direction) is 30 m/s (magnitude). A vector quantity has more than one dimension of description. A vector quantity can also be resolved into 2 components, like x and y components of velocity.

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