When working with position/time graphs of accelerated motion, it is easy to confuse the dire

ction of velocity with the direction of acceleration. for example, look at the two graphs below:

Many students will instinctively say that the first graph is positive acceleration, while the second graph is negative. In fact, *these are the same graph*, as you can see here:

It is a single parabola, representing positive acceleration.

So how do I get kids to recognize positive and negative acceleration? Using the following, stupidly simple trick:

It’s really that simple. Any part part of the smile, be it a corner of the mouth smirk or a full on grin, still looks positive. Any part of the frown still looks negative. And that’s it.

leetrampI’ve been using this for a few years, and I also find its simplicity helpful to students. We recite, “Smiley face, positive Attitude/Acceleration; frowney face, negative Attitude/Acceleration.”

I love the title you chose for this post ☺