# Tracker Video: calibration point pairs

I was going to make this as a video tutorial, but it just didn’t work out right. So, here it is in blog post form. How do you deal with a video that zoom and pans at the same time? You could keep on adjusting the coordinate axis AND adjust the scale for each frame…

# How do color filters work?

So you have seen these color filters (or gels as they are also called). When you look through a red filter, everything looks red. What do they do to the light? I am not going to tell you the answer. However, I will show you some examples so that you can figure out the answer…

# Hug a Laser

It is my duty as a blogger to mention lasers in this time of international laser celebration. This May is the 50th anniversary of the first lasers. Everyone knows a laser that they love, right? We all use them. So, instead of talking about lasers, I am going to post some great links to other…

# Why is it dark inside?

This was a great question. When you come inside after playing in the sunny outside, why is it so dark? Simple answer: because your eyes are smart. When you are outside, there is a lot of light. Really, it is too much light. To compensate for this, your pupils (the part of your eye that…

# Diver in a bottle

I am surprised at how many people (chemistry faculty included) have never seen this demo. (oh, technically it is called a cartesian diver demo) Basically, you put some floating object that has an air space in a closed bottle of water. When you squeeze it, the diver goes down. For my setup, I used a…

# Pressure demo: suction

How does a suction cup work? It is all about the atmosphere. Here is a demo. Take some type of “suction cup” device. In this case, I used a toy dart. Stick it to something smooth and lift it up. Like this: What lifts up the metal block? The atmosphere. Diagram time: But this isn’t…

# Activities for Pi Day

Oh, I know you missed it. Really, it wasn’t your fault. Pi day fell on a Sunday, so how are you supposed to have pi-day activities in class? Don’t let it stop you. You are better than that. Do the activity anyway. What to do? Here are some suggestions. (Suggestions aimed mostly at the high…

# Tablecloth and dishes trick – the BMW version

Hat tip to Frank for sending me a link to this video: If you have never done a demo like this (without the motorcycle), you should. It really isn’t too difficult. Here is a video of my version: Inertial demo from Rhett Allain on Vimeo. So, the question is: is the motorcycle thing real or…

# DIY Force probe

I was thinking about some experiments that deal with friction and I wanted to show something with a force probe. The problem is that most people don’t have one of these. So, I decided to try and make one out of simple things. In this case, I am using some straws, a rubber band and…

# Green Laser and Fluorescence

Do you have a green laser pointer? You should. They are relatively inexpensive now. What if you take your laser pointer and aim it at stuff in your house? The laser dot always looks green, right? This is actually a pretty important point about color. Suppose I have the lights on in a room and…