Often in physics class I like to demonstrate or have the students model what we are discussing in class. Since today was the first day back form holidays, I was totally unprepared and the demo that I quickly tried to throw together miserably failed. I asked the students to go to the PhET Interactive Simulator to try and model what I failed to do and it worked beautifully. Since half the class had laptops, it was quite easy to ask them to go to the website and play around with the simulator to model what we just discussed. I typically just show the class the website and not have them play with it because its just too much trouble to get the laptop cart for a 5 min activity. But now that they are consistently bringing laptops to class, it is much easier to use this online tool. Now I just hope that my other class brings in laptops tomorrow.