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.
