Tag Archives: physics

one week of teaching with portals

Here are three student made levels from the first week of playing Portal 2 in physics. You’ll see they’re simple with extraneous objects and obvious objectives, which isn’t surprising given that they had only played about two hours of Portal 2 before making these. To be clear, these weren’t for any particular experiment in class. Students made these as first attempts at making puzzles.

It’ll be interesting to compare these novice levels to what they make after they familiarize themselves with Portal 2. I’m excited to see how they progress.

Overall, I’ve seen some interesting reactions from the kids. For the most part, they seem pretty enthused. They’ve been explicit about how they appreciate applying what we learn in lecture to what they can do in the game. I even had a student tell me that she enjoyed using math for the first time when she used data from her own experiments to calculate the strength of gravity. Students have made comments about how engaging physics lessons are with the puzzle maker, and I’ve had numerous kids tell me they’re looking forward to physics class, which makes me feel pretty good!

So far we’ve run through a few labs where they’re building really simple experiments in the puzzle maker.

Gravity Lab:

In this lab, students are measuring the distance and time of a fall to calculate the strength of gravity in-game. The students who fell the farthest measured the most accurate measurements so far. Without an in-game timer, students have to use a regular stopwatch to calculate the time of their falls. Unfortunately, they aren’t the most careful bunch and tend to be off by a sizable fraction of a second each measurement. That kind of error wreaks havoc on measurements when the fall time is only about half a second anyway. They need a long fall time to minimalize issues from their reaction times.

Class average:

5.3 panels/s^2 (actual value: 4.7 panels/s^2)

Terminal Velocity Lab:

In this lab, students are calculating terminal velocity by measuring time and distance as they fall in an infinite loop. They then repeat their experiment with a cube. When I originally wrote this lab, I hadn’t considered the idea that portals could impact velocity. Since then, I’ve found that portals slow objects down, which almost makes this lab pointless. However, I still taught it as practice for data collection and to identify that cubes are subject to a bit more friction than players (I think). Either way, this lab easily led into a useful discussion about the effects of friction and air resistance.

Class 1 averages:

Chell: 10.8 panels/s          Cube: 9.8 panels/s

Class 2 averages:

Chell: 10.8 panels/s          Cube: 10.8 panels/s

Tagged , , ,


I’m feeling really good right now. After about a year of work, I finally got a full class of students playing Portal! My physics students played Portal 2 for an hour in class yesterday. On Friday, they’ll be doing their first lab (on gravity). Keep an eye out this weekend for some student made experiments!

Tagged , , ,

do portals slow you down?

Note: for folks coming in from Wired, here’s the thermodynamics of the ideal gas law video.

Fun with slow motion cubes, graphs, and data! I like this video a lot.

Console Commands:

sv_cheats 1 (only needs to be done once)
noclip (lets you fly around the room)
phys_timescale 0 (freezes objects in the game)
phys_timescale 1 (lets objects move normally again)
phys_timescale 0.25 (slow motion cubes!)
impulse 200 (removes/replaces portal gun)
bind “z” “noclip” (an example of linking console commands to keyboard shortcuts)

Tagged , , , ,

hello wired

Hello folks visiting from Wired’s Game Life! Glad you could stop by. Here’s a little more about the thermodynamics of the ideal gas law.

I’m adding new videos and demonstrations as quickly as I can. You can find most of them linked at the top. Check back later for another look at the way friction slows down airborne cubes. And if you’re an educator, check out my lesson plans on Teach with Portals. I’d love to get any feedback you might have!

Tagged , ,

conservation of momentum and collisions

Do mass and velocity play a role in the outcome of collisions? Let’s find out.

We’ll be colliding three objects: a cube, a sphere, and a turret. A cube has a mass of 40 kg, a sphere has a mass of 75 kg, and a turret has a mass of 100 kg (found by using the console command physics_debug_entity while looking at an object). If all goes well, the object with the larger momentum due to its larger mass or greater velocity should send the other object flying backwards as the result of their collision.

Test 1: Two cubes of the same mass hitting at the same velocity.

Their identical momenta cancel out.

Test 2: A sphere striking a lighter cube at the same velocity.

The sphere’s larger momentum causes the cube to fly backwards.

Test 3: A cube striking a turret.

The turret has a larger mass and its momentum causes the cube to fly backwards.

Test 4: A sphere striking a turret.

The turret has a slightly larger mass and its momentum causes the cube to fly backwards.

Test 5: A fast cube strikes a slower cube.

The fast cube’s greater momentum knocks the slower cube backwards.

It looks like mass and velocity are significant factors in collisions and handled correctly (at least superficially) by the Source engine.

Tagged , , , ,
%d bloggers like this: