Question Video: Determining Whether Velocity Is a Vector or a Scalar Science

Is velocity a vector quantity or a scalar quantity?


Video Transcript

Is velocity a vector quantity or a scalar quantity? (A) Vector, (B) scalar.

The velocity of an object is equal to the change in its displacement divided by the change in time. Recall that displacement is the straight-line path between two points. It is important to recognize that the object must travel from one point to another. The object has an initial position and a final position. And therefore, displacement has both a magnitude and a direction. We can recall that a vector quantity has both a direction and a magnitude. So, displacement is a vector quantity.

But what does this tell us about velocity? Well, time is a scalar quantity; it only has magnitude. When we divide a vector quantity by a scalar quantity, it leaves us with a vector quantity. So, displacement, which is a vector quantity, divided by time, which is a scalar quantity, gives us velocity, which must be a vector quantity. This tells us that velocity has both a direction and a magnitude. This is different to speed, which is a scalar quantity and therefore only has magnitude.

For example, if an object is traveling from left to right at 20 meters per second, we know that it has a horizontal velocity of 20 meters per second, because we have specified both its direction and its magnitude. When we refer to the speed of the object, we’re only thinking about magnitude. So, the object’s speed is just 20 meters per second. So, the answer to this question is answer option (A). Velocity is a vector quantity.

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