Dot Physics

Archives for March, 2009

What is a fake force? A fake force is one of those forces that introductory texts tell you aren’t real – like centrifugal force. They aren’t real in the sense that they are due to one of the fundamental interactions. Basically, introductory texts (and even blogs like this one – not a bad summary of…

Tom and Jerry, or Fetch! with Ruff Ruffman? Answer: Tom and Jerry. What? Yes. The reason: Tom and Jerry has bad physics but does not pretend like it has good physics. I know this is probably going to “type-cast” me as “that guy that keeps attacking Ruff Ruffman.” Soon to be followed by “Leave Ruff…

Analysis of Dan Meyer’s photo.

Dan Meyer made this awesome photo. He posted it so that others could look at it and come up with lesson ideas to use with this. There are some very good suggestions in his comments. I wasn’t going to analyze this because I didn’t want to rob some students of the opportunity, but I can’t…

A blanket and cold stuff

There are some really cool questions out there. Questions that do not require a lot to ask and do not require a lot to answer. Here is one such question (I can’t remember where I first found this question or something like it): Suppose you put take two identical cans of soda out of the…

A physics question. Answer quick!

I have always wanted to ask a question like this – but never found the right test for it. Perfect for a blog. Question: Suppose you are in your car at a stop light behind a truck. The truck is pulling a trailer with a rollable tractor on it. When the light turns green, the…

So, I was in the student computer lab helping a student with a numerical calculation. I couldn’t help notice the student next to me was registering for classes. Here is here strategy: Look at required courses. Check available classes. Check ratemyprofessor.com. Re-check available classes. Repeat. So? What is wrong with this? I see a couple…

I just got back from judging elementary level science fair (this is like kids in 6th grade or something). Here are some quick notes in no particular order. Please, please do not have a 20 item list of supplies that you used on your board including things like thumb tacks, tape, paper and poster board.…

Dear Ruff Ruffman, My kids really like your show. However, there is a problem. You promote it like it is science, but the content keeps having mistakes in it. Previously, I pointed out your mistake about in infrared thermometer (if can’t remember, you said the thermometer measures the temperature with a laser. In fact, the…

Better technology sometimes causes problems. In this case, technology has made video cameras really small. Small? That’s a problem? Well, the problem (as I discussed previously) is that small cameras are not stable and make “shaky” videos. Well, then increase the mass of the camera – simple. I wanted to test this idea and make…

I previously talked about measurements (some) when I looked at the uncertainty in the distance to the Sun. One of the simple ways of determining the uncertainty of a calculated quantity is to use the uncertainty of the measured variables and find the max and min that calculated quantity can be. The example I used…