I was teaching centripetal acceleration to my 10th grade sister several weeks ago. I used the race car on a banked curve explanation in another blog entry. We got to the end and she said something to the effect of, “Oh, I get it. That makes sense. Except — what’s a vector?”

I had to think for a moment. Outside of the physical science and mathematical world, what is a vector?

Finally I explained it as follows:

You’re having a picnic at the park. Just as you’re about to leave, you realize you don’t have any mustard for your hot dogs. So…you go to the store on your way to the park. Or…you could have just checked the back of the cupboard and realized you had some. Then you can just go straight to the park.

But the main thing is: you still made it to the park, right? So regardless of whether you stop at the store first, or not, you still have a picnic at the park.

My sister’s face lit up as she realized vectors were not the same as triangles (she’s currently in geometry) and she acknowledged that vectors and their resultant are all different ways of expressing the same thing.

Mathematically:

2+3+1=4+2=6