I’m at GLS in Madison, WI currently. Leslie Redd, Steve Isaacs and I will be hosting a workshop on teaching with Portal 2 at 2pm today. Tomorrow, we’re presenting at 4pm as part of the Computational Reasoning panel. Hope to see you there!
Interview with Daniel V part 1
Teachers aren’t the only people trying to get Portal 2 into classrooms. It’s only natural that students too are pressuring their teachers and schools to try out video games in the classroom. One 11th grade student, Daniel Verlaque, was instrumental in bringing Portal 2 to physics classes at his school. And students at other schools need to thank Daniel, too, for providing technical support to Portal 2 educators around the world on Valve’s Portal 2 teacher forum!
I’ve been impressed by how hard Daniel has been working to get teachers to try Portal 2, so last week, I sent him a few questions about his thoughts on using video games as teaching tools. Here is part 1 of his (slightly edited) responses.
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How did your interest in teaching and learning with Portal 2 begin?
I’d never even heard of Portal until Portal 2 came out. One of my friends kept telling me about it, which interested me, but my mother had always been set against video games, so I never thought I’d get it. However, she happened to read a New York Times article that convinced her to let me buy the game. I instantly fell in love with Portal 2 and became a huge Portal fan.
Fast-forward a bit, to the beginning of the 2012-2013 school year–and my first high school Physics class. My Physics teacher is a very friendly guy who likes technology and actually wrote his thesis on using video games in classrooms. When I asked him if he’d ever played Portal 2, he said that he had, but he didn’t seem to think that we could play it in class because of cost and deployment issues. However, when I came across the teachwithportals website and discovered that Portal 2 was actually free for school use, he said that he’d love to give it a shot, as long as the tech department was OK with it. Over the next few months, I demonstrated Portal 2 (and Universe Sandbox 2, which was also available through Steam for Schools) to the tech department and then worked with them to deploy and test the software. Despite some obstacles, we eventually managed to get Portal 2 and Universe Sandbox 2 installed on all of our science department’s laptops.
Which classes are using Portal 2 [at your school]? Are students learning with any other video games at your school? How are classes that use video games different than traditionally taught classes?
At the moment, Portal 2 is not a widely used program at my school, in large part because it was only deployed halfway through the school year. My teacher’s classes played Universe Sandbox and Portal 2, but none of the other teachers have used them because they are not yet familiar with them. I will probably show the rest of the physics teachers how the programs work sometime in the near future so that they can decide how to incorporate them into their classes.
We played Universe Sandbox in January, at the end of our unit on gravity. Although we didn’t actually use it to learn the material (simply because the curriculum had been planned without Steam for Schools in mind), we did get to play it after the test, while the concepts were still fresh in our minds. It was really quite a lot of fun to watch the other students play Universe Sandbox for the first time and see the concepts they’d been learning from a blackboard come to life in a 3D virtual universe. I’d first played Universe Sandbox several months before we even learned about gravity, so it was especially interesting for me to see how my own understanding of the physics behind the game changed.
If you were teaching [insert any subject here], how would you teach with Portal 2 or other video games?
I’m going to stick to what I know–Portal 2 and Universe Sandbox in Physics–and say that I would use them to help demonstrate concepts to students and (when appropriate) use them to replace some of the labs we do in class. Instead of just drawing something like projectile motion on a blackboard and leaving it at that, I’d show the students what the concepts look like in an immersive 3D world. Universe Sandbox is especially interesting, as it’s really impossible to model a system of that scale in a lab experiment. When we learned about gravity, we were limited to drawings on the blackboard and a few (very simple) online animations. But with Universe Sandbox, a teacher can have his or her students actually understand what would happen if, for example, the Earth’s mass was changed to equal that of the Sun, or what would happen to Saturn’s rings if another planet got too close. These are things that you really can’t demonstrate on a blackboard. With something like projectile motion, you can at least draw a parabola on the board–which still pales in comparison to something like Portal 2, but at least you can do something–but there’s simply no way you can draw Saturn’s rings being ripped away by a rogue planet or a collision between two galaxies.
What advice would you give to educators who want to teach with Portal 2 or other video games?
The most practical advice I can give to educators is that they should try to avoid rushing into the setup stage. Make sure your IT department is on board and you have a good idea of what you’re trying to do. You’ll run into obstacles, but don’t get discouraged–there are lots of people who are willing to help you out!
sunday miscellany
1) I’ll be presenting at Games+Learning+Society with Steve Isaacs and Leslie Redd in June. We’ll be presenting our work on teaching with Portal 2 and running a workshop where educators can explore the Puzzle Maker and develop lesson plans to share and take home. You should meet us there!
2) A Portal themed web series? Ok, so it looks really dorky and cheesy… but it’s Portal! I’ll at least watch the first episode.
3) Check out GlassLab’s work with SimCity EDU. Very cool way to teach civics, social studies, the science behind running a city and probably a few other subjects as well. I fully support this kind of work.
Portal 2 at PAX East and Data
Two things:
1) Lisa Castaneda and Geoff Moore recently spoke at PAX East about teaching geometry with the Puzzle Maker. I love the idea of “broken levels,” where students have to finish building levels with certain restraints.
2) Here’s the data I used to analyze projectile motion, in case anyone ever wants to do their own data analysis: Portal 2 Position Time Data, Portal 2 Velocity Time Data.
Projectile Motion in Portal 2 – part 3
And finally, let’s take a look at air resistance. Do falling objects in Portal 2 slow down due to air resistance?
Short answer: Yes! The Source engine accurately handles air resistance and terminal velocity!
Long answer:
Air Resistance and Terminal Velocity Background
Terminal velocity follows naturally from comparing forces acting on an object. As Newton’s first law explains, objects change the way they move only when acted upon by an outside force. For instance, a hockey puck is perfectly content sitting still on the ice so long as no forces are acting on it (as if we could speculate about the mindset of an inanimate object!). As soon as a force acts on it, perhaps in the form of a slap shot, it starts to move. The puck will maintain the same velocity until another force, let’s say the goalie’s glove, changes its velocity. To be even more precise, unbalanced forces cause changes in velocity. That is, multiple forces can act on an object without causing an acceleration so long as the forces balance each other out. In tug-of-war, for example, two teams may be enacting tremendous forces on a rope, but so long as both teams create the same force in opposite directions the rope doesn’t budge. As soon as one team pulls harder than the other, the forces become unbalanced and the rope’s velocity starts to change.
In the hockey example above, we assume the ice and air around the puck produce negligible friction on the puck, a tactic often employed by physics problems. In reality, the situation is more complicated. Any object moving through a fluid, such as air, or in contact with a surface, such as ice, feels friction. Friction is a unique force in that it always opposes motion. Without motion, friction does not exist. Unlike other forces, friction can never cause motion. As an object’s velocity increases, so does the force of friction.
In an situation analogous to tug-of-war, a falling object feels opposing forces. Gravity accelerates the object downward while air resistance accelerates the object upward in the form of friction. As the falling object gets faster, friction from air resistance increases. Eventually, the frictional force matches the gravitational force and the object no longer accelerates. At this point, the falling object has reached its maximum velocity, which we call terminal velocity.
The velocity of an object in freefall will generally follow the relationship below:
[equation 1, credit to Wikipedia]
where m is the mass of the object, g is acceleration from gravity, ρ is the density of the fluid (typically air), A is the cross-sectional area of the falling object (or the surface area of the side of the object facing the direction of motion), and CD is a dimensionless constant called the drag coefficient. Notice in this equation that mass is a factor, and a more massive falling object should fall faster than a lighter counterpart.
Terminal Velocity in Portal 2
Once again, we want to collect data from Tracker and fit a curve to it with Gnuplot. This time we’ll be looking at velocity as a function of time and trying to fit it to equation 1. We’ll use Gnuplot to fit the data to a function of the form of
[equation 2] v(t) = -B*tanh(C*t),
where B and C represent the constants before the hyperbolic tangent (tanh) and inside the hyperbolic tangent of equation 1 respectively.
Holy cow. The velocity of a freefalling 55kg contraption cube almost perfectly follows what you would expect from equation 1 (note: this graph lacks uncertainty). We can confidently say that the Source engine mimics air resistance!
We’re left with an interesting situation, though. On the one hand, we have data that clearly show that whatever algorithms are controlling motion in Source accurately represent air resistance. But now we have to wonder about the constants within equation 1. We know Source scales terminal velocity to mass. But is Source using a realistic value for air density in the game? Is it really taking the cross-sectional area and drag coefficient of the cube into account?
For now, we can check if Source is at least internally consistent, regardless of whether or not it uses accurate values for the constants in equation 1. Let’s assume that Source uses some constant to account for drag coefficient and air density. We already know mass and gravity. So let’s solve for the cross-sectional area. Gnuplot solved equation 2 with B = 318.6 and C = 0.4768. If we equate B to the constant before the hyperbolic tangent in equation 1 and solve for the cross-sectional area, we get a value of 0.121 u2. Plugging in our value for cross-sectional area to the constant inside the hyperbolic tangent, C, and using all of the same values for ρ, CD, m, and g, we get C = 0.477, which is exactly what Gnuplot produced. So, at least Source is in some way internally consistent.
To be continued with a wrap up of projectile motion…
