What happens when, if travelling forward at 100 km/hr, you throw something backwards at 100 km/hr?
It may be tricky to demonstrate in class, so here are a couple of useful resources.

From a Japanese TV show – a real life example of adding vectors and relative motion. Scroll forward to the 3 min mark if this doesn’t happen automatically.

Then Mythbusters wanted to try it

Can you explain why?

Isn’t Physics just mad Ted?

Now for something completely different (well there are some references to direction in there, so it just about qualifies).

Links to each of these resources are available on the Vectors page of thephysicsteacher.ie