We did physics speed dating (see this blog post by Kelly O'Shea if you want to know more) to tackle the most complicated constant velocity representations we'll do. I have to be careful at this time of the year; I can spend a lot of time making sure their model of constant velocity is perfect, but I don't think it really matters for a few reasons:
- We will get a chance (literally in the next unit) to deepen our understanding of these representations.
- It takes a lot of effort to get the last bit of refining. Do I care what they do on motion maps with the last dot? Well, no, not really. If a student decides to draw the position-time graph one more second to what the arrow says will happen next, I'm OK with that. I'm sure other physics teachers have strong opinions about this, but I don't, and more importantly...
- I don't know what we'd get out of having the best constant velocity model. Constant velocity isn't the cornerstone of physics. The next model is. I don't care if there's a small mismatch between my model of constant velocity and theirs.
Still, even with this leeway, we still have some important discussions:
- Where does a position-time graph? Does it always start on the vertical axis? Does it always start with the first dot?
- What happens between one region of constant velocity and another region? How can the velocity change and no time pass?
- What do the numbers on the motion map diagram represent?