# Dot products

Discussion in 'Mathematics' started by matqkks, Jul 1, 2011.

1. ### matqkks

<h3 class="groups">How can I make something like dot products tangible?
Are there real life examples where dot products are used?
This is for motivating students. Aware that we can test for orthogonality.
</h3>
Thanks in advance for any replies. Really appreciate anyone taking time out to answer these questions.

2. ### DMNew commenter

Finding the angle between two vectors? You couldn't get more basic than that surely?

3. ### ResourceFinder

LoL

My thoughts exactly

4. ### Betamale

Is it? do some not just enjoy the topic in the context of maths and problem solving sometimes?
As stated above, its not a hard topic to find countless examples of but what happens when you need to 'motivate' students with something a little more obscure?
"We are learning the cosh function so you can see what happens if a seagul sits on a telgraph wire sometime"
Why not just enjoy some maths for the intrinsic value of proof and manipulation?

Work done = Force . displacement

6. ### ResourceFinder

Well in that case

Magnetic Flux = (Magnetic Field) . Area

7. ### D Franklin

If your students are also interested in computing, then game-physics and ray-tracing use a lot of dot-products, typically in a somewhat more advanced way than you'll see at A-level.
E.g. A ray has equation x = p + tr. Does it intersect the sphere with equation |x - a| = R, and if so, where?

8. ### DMNew commenter

then
Electric Flux = (Electric Field) . Area

Well, in that case:

Aeon Flux = Charlize Theron . Area

10. ### ResourceFinder

LoL

Now that will excite the OP's students

11. ### DMNew commenter

Are we discussing energy states now?

12. ### PiranhaStar commenter

Maths for its own sake is great, but I see no harm in at least mentioning a use for something even if it is beyond what they will cover at A-level. I don't want to be the sort of mathematician who thinks that a branch of Maths is somehow sullied if an application of it is found. The "why do Maths at A-level" question is often answered with the many careers it is used in. When a student asks "what is the use of this" in a constructive way, I like to be able to give them an answer.
BTW, thanks for the ideas on the use of dot products. I could only think of a couple myself.

13. ### ResourceFinder

I just say

Mr RF writes software for computer games ... he uses "insert bit of pure maths" ... always a winner