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# Acceleration as a Vector

### Acceleration as a Vector

The "direction" of acceleration is whether acceleration is positive or negative.

*Acceleration is a* * vector* **

**, which means it has both a magnitude and a direction.**

**quantity**Acceleration is a vector quantity, so it has both a **magnitude** and a **direction**

This woman is going from a speed of $3 \space m/s$ to a speed of $7 \space m/s$. Is she speeding up or slowing down?

The woman is speeding up from $3 \space m/s$ to $7 \space m/s$

She does that over the course of just **one second**, so her acceleration is $4 \space m/s^2$

Now the woman is going from a speed of $7 \space m/s$ to $3 \space m/s$. Is she speeding up or slowing down?

The woman is now slowing down again from $7 \space m/s$ to $3 \space m/s$

She does that over the course of just **one second**, so her acceleration is now $-4 \space m/s^2$

Acceleration's "direction"

What do you think we mean by the "direction" of acceleration?

When an object is **speeding** **up**, acceleration is _______________.

When an object is slowing down, acceleration is _______________.

Summary!

So the "direction" of acceleration refers to whether acceleration is positive or negative

If **positive**, like $4 \space m/s^2$, the object is speeding up.
If **negative**, like $-4 \space m/s^2$, the object is slowing down.