rallain | April 13, 2009Previously, I showed how to analyze a cat video with Logger Pro. Logger Pro is nice, but so is Tracker Video. I also posted a comparison between Tracker and Logger Pro. Now, here is the same tutorial on the same video using Tracker Video.
Record your screencast online
I am not going to go through the analysis, since it would be the same as with Logger Pro.
rallain | April 12, 2009I already talked about increasing the temperature of a pool. My father commented that he thought the pool level rose by like half an inch when the temperature increased (by about 10 degrees F). So, this leaves the question: Is my father crazy, or is this possible? Or are both true?
Does water expand when it warms up? Yes, except when it melts. Why does this happen? Liquids are actually very complicated, but here is a basic answer. Take a look at this PhET gas simulator, I know it is for gases not liquids. I think we can make it behave like a liquid if you increase the gravity to the…
rallain | April 11, 2009It is spring break, so we are at my parents house for a couple of days. The kids like it because there is a pool, a heated pool even. It really isn't that cold outside, but yesterday the water measured at 62 oF. So, with some help from the kids, we cleaned out the pool and turned on the heater. We also put a cover on it, hopefully to help it heat up some more.
This is perfect for a quick calculation. Is it reasonable that the pool could get up to a swimable temperature by tomorrow? Let me first make some assumptions and data:
15,000 gallons of water in the pool. This is about 57 m3.…
rallain | April 10, 2009I am so pumped up that MythBusters is back on. Not only do I like the show, but it offers so many blogging opportunities. Their latest show featured car crashing myths. One of the myths from the episode was a redo of the myth where two trucks crash head on simultaneously crushing a smaller car in the middle.
The first test was very similar to the previous time they tested this, but faster. They towed two 18 wheelers to crash together around 50 mph and smash a stationary car. The results were impressive. However, they did not have the result of the car completely contained in the…
rallain | April 9, 2009This post has nothing to do with physics, so if you are only into physicsy stuff, skip this. The primary goal of this post is to list what I need to blog. The secondary goal is to rant about my laptop.
I destroyed my laptop (well, not really, but kind of). Basically, I had a tooth pulled on Tuesday. It wasn't bad, really it wasn't. The doctor said I should be ok to teach lab after the pull, so I did. NOTE: DON'T EVER DO THAT. Teaching lab after getting a tooth pulled = bad idea. Really bad. Nothing like not being able to talk while drooling blood. I think I scared my students.
After…
rallain | April 7, 2009I recently posted a tutorial on using Logger Pro for video analysis. Why did I use Logger Pro? Why not Tracker Video? Here is a quick comparison of the two.
Logger Pro
In the previous tutorial, I used Logger Pro. The primary reason was that the tutorial was for a lab course. The students were already familiar with Logger Pro. Here are some of the pros of Logger Pro.
Fairly straight forward to use.
Good graphing and curve fitting utilities built in.
Integration with data from other sources. If you video a ball falling and also use a motion detector, you can "sync" the data.
Not really a…
rallain | April 7, 2009Dan Meyer at dy/dan just posted about teacher-student analogies. His analogy is that the student is like a weight lifter and the teacher is the spotter. I like this. It is similar to my usual analogy that the teacher is like a trainer and the student doing some exercise. Another analogy I often use is a person learning to ride a bike. The learner is the one doing stuff, not the "helper" or "facilitator". I am really not sure what to call the helping person. Maybe the Yoda would be a good term. I like that.
Look at a person learning to ride a bike (btw, here are my tips for learning to…
rallain | April 6, 2009Cats can be entertaining - especially when they are someone else's cat and that someone made a video. Really, this post is about analyzing video with Logger Pro (in a tutorial type fashion). I just happens that I chose this cat video to analyze. Here is the video:
I am going to look at the part where the cat gets on the fan. I will try to step through the analysis so you can do your own.
Get the video
Actually, the first step is to find a video. YouTube has tons of stuff. Also, you could make your own video with a camera. A couple of things to make your life easier:
A non-zoom video.…
rallain | April 3, 2009I found this video to be very entertaining.
Dry Ice is LEEEEEEATHALLY DAAAANGEROUS? - These bloopers are hilarious
William Beaty's site has tons of great stuff - http://www.amasci.com/
rallain | March 31, 2009What 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 real vs. fake forces) attack the centrifugal force. This is because it is so common for students to want to use these faux forces in the wrong way. Better to just not use them at all.
Anyway, there are times when faux forces are awesome. Just to be clear, a faux force is needed to use normal…
rallain | March 25, 2009Tom 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 ALONE!" I am sorry, I can't help it. Here is my problem. If you are going be a show, do whatever you like (I might still make some comments). If you are going to be a show that attempts to teach some stuff, don't you think you should get it correct or at least not reinforce bad ideas?
The…
rallain | March 25, 2009Dan 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 resist. Also, I doubt the first step a student would use would be to google for the answer. HA! I just caught you, you googling student.
Ok - I will try not to post any data. However, I will post some info on how I analyzed this.
The photo is a composite image from a video clip of a person throwing a…
rallain | March 24, 2009There 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 fridge and place them on the floor in the middle of a room. One can you leave alone and one can you cover with a wool blanket. After an hour, you come back and check on the two cans of soda. Which will be warmer?
First, why do I like this question? Mainly because everyone can give an answer. If asked…
rallain | March 23, 2009I 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 truck starts to accelerate. However, the cable holding the tractor to the trailer breaks and the tractor starts to roll off the trailer. You are right behind the trailer. What do you do?
Do you have an answer yet? You should probably come up with one quickly. That tractor is rolling off now. I will put the answer…
rallain | March 20, 2009So, 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 of problems. First is the reliability of ratemyprofessor (RMP). I have not looked at my ratings on this site in a long long time, but I am sure they are not accurate. My favorite RMP comment: Dr. Allain teaches astronomy 101 like it was a 400 level…
rallain | March 19, 2009I 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. And then please do not read this list aloud during your presentation. I know you are nervous, I feel for you. Maybe you are trying to fill up time - maybe you think a long presentation is a good one. However, don't do it. Stick to the important stuff. If you need to fill up space on your…
rallain | March 17, 2009Dear 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 laser is just used to aim.)
So, you see, I don't just like to randomly attack people. The problem is that you are saying "hey look at science" but your science is wrong. I suggest you either a) stop pretending to be a science show or b) get a science advisor (I am…
rallain | March 16, 2009Better 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 a test video with and without extra mass on the camera. I was thinking - what could I attach to it? A 2 lb or 5 lb scuba weight came to my mind. Then it hit me: a water bottle.
When do people use these little video cameras? To film their kids or something? If…
rallain | March 16, 2009I 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 was in calculating the uncertainty for the area of a rectangle. So, the maximum and min areas would be:
And then the uncertainty in the area can be described as:
Yes, I know this is not as sophisticated as the normal procedure for error propagation, but it works. This is the…
rallain | March 14, 2009I don't know if you noticed, but this blog has been down almost a week. Several things happened. First, I was hosted by Lunarpages. That didn't go so well. They ARE cheap, but maybe that is for a reason. I won't really go into details except to say that they have CPU limits, but you can't really see your usage.
The next problem was that I decided to move to slicehost. Slicehost basically gives you a virtual linux server, but you have to do all the servery stuff. I thought I was up to the task, but apparently not. Setting up a linux server (to me) is like trying to put together a LEGO…