Best fit Groke
After my recent experiences with simulations I decided to go back to nature by throwing real balls around the classroom to introduce the topic of projectile motion. I recorded the motion with my webcam and plotted graphs (using LoggerPro) to show that the horizontal motion was constant velocity and the vertical constant acceleration. Worked great. Even got a value of 9.8 ms-2 from the best fit parabola. Towards the end of the lesson, after working though the algebra and some examples, I repeated the experiment with a balloon. As you can see I was a bit sloppy placing the markers and got some spurious results. I was marking the front of the balloon which wasn't a good idea, the balloon rotated during flight resulting in the two kinks. This graph clearly isn't a parabola but what is it? Ismar was quick to suggest that it's a Groke and if you reveal the hidden image below you will see he is right.
