### Wolfram Alpha Widgets

Try to say that 5 times really fast. Go ahead, try it. Well, at least it is not as difficult as Fox in Socks - man that book is a killer. This WAW is basically a means to embed Wolfram Alpha queries into a webpage. Pretty cool idea, but I am not sure how well it does the job. In fact, I have tried to embed calculations in my posts before. So, how about I just give a quick review of some different ways to do this. For all these methods, I will put in a calculator to determine the density of something given its mass and volume. Javascript version Density calculator Enter the mass: kg…

### How far will the car go?

Honestly, I was going to add this to my previous post about the jumping car but I didn't because I wanted to finish. So, here it is and more. Actually, I will just make a projectile motion spreadsheet. That way, anytime you want to do a projectile motion problem, you can come here. Maybe this is a bad idea, but I am going to do it anyway. To start with, I will just say that for projectile motion the horizontal and vertical motions are independent (except for the time it takes). If you want a refresher on projectile motion, here you go. Oh, a couple of assumptions: Object starts at x = 0…

### Preemptive MythBusters: Giant Water Slide Jump

I am excited. This Wednesday, the MythBusters are doing the giant water slide jump. Maybe you are new to the internet and you haven't seen this video. Here it is: And since it is as old as the hills, of course I have already analyzed it - actually twice. First, the video is fake - but it is an excellent fake. Here is another site with details on how this was created. What did I look at in my previous posts? Here is a summary. The video is difficult to analyze because of perspective changes. Even with these problems, nothing says it has to be fake. The vertical acceleration during the…

### 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 school level) Plot Diameter vs. Circumference This is a great one. Let your students find as many round things as they can (cylinders work the best - or flat stuff). Measure the circumference (you can use a string or a tape measure) and the diameter. Since the relationship between these two is…

### Pendulum, let it go

This is a requested post. Clearly, I do requests. The idea here is that I am going to give all the details needed to determine the equation of motion (and then model it) for a basic pendulum. Warning: this post is a little more advanced than my normal posts. There are some prerequisites. You need to understand derivatives. I will assume that you do. Here is a pendulum. (and this time I will stick to my variables) Like I said before, this is a tricky problem unless I use some tricks. The problem is that the tension the string exerts on the mass changes. Here is my trick: think about a…

### Uncertainty and Video Analysis

This is for commenter JimP. How do you take into account uncertainty when using video analysis? A great question. The first thing to think about is where does the uncertainty come from? My first guess would that it would be from the user. Where does the user click? Is it right on the object in each frame? Is the scale set correctly? I guess there could be other sources of error - maybe there are repeating frames that are a result of encoding. Maybe there is interlaced video frames. Well, what to do? I will just look at one motion in particular and do the analysis several times. I…

### Uncertainty in measuring the launch speed

This is really a lab that I have students do, but I am pretty sure they don't read this blog - so it is ok. If they are reading this, hi! We have these projectile cannons that shoot small balls. In order to look at projectile motion, they need to first determine the launch speed of the ball. I have a great method for this. Basically, shoot the ball horizontally off the table and measure how far horizontally it goes. You can get the final location of the ball by having it hit a piece of carbon paper on top of normal paper. If you don't know what carbon paper is, you are young. Anyway,…

### Snow Board Jump Help

I really shouldn't do this. I might be helping someone to set up something dangerous. But, I am going to anyway. Here is a question posted on some forum. (actually, it is from math help forum) "I'm anticipating a good winter this year, one with lots of snow. My yard is sloped quite a bit and it would be the ideal place for a huge snowboard jump, only problem is I need to calculate how fast I will be traveling when I hit the jump, how high and what angle the jump should be, and the distance and angle of the landing ramp to optimize my range." So, what am I going to do? I am going to give…

### Numerical Calculation in Open Office

I created another screen cast showing how to get started with a numerical calculation for one of my classes. In this case, the students are attempting to model the motion of an object falling with air resistance. The following example doesn't show the steps including the air resistance, but maybe it is enough to get someone started. Record your screencast online

### How much would "free" energy cost you?

This was on my 'to do' list, but Tom at Swans on Tea beat me to it. Basically, this grocery store has these plates that when depressed produce electrical energy. Tom does a good job pointing out that this is not free energy (the original article says this also). Clearly, the energy comes from the cars. How much would this cost the cars? As always, let me start with some assumptions. The original article says that the bumps will generate 30 kW of energy every hour. That is an odd thing to say. I am going to interpret that as 30 kW of power for all hours (every hour). They couldn't have…

### Mythbusters and WANTED - curved bullet

I have been wanting to look at this whole curved bullet thing, but I wasn't sure how to approach it. In case you are familiar with the myth, this is from the movie WANTED (which I did not see). Apparently, some people learn how to make bullets curve by moving their gun. Here is a shot of a bullet curving in front of someone. Maybe the picture doesn't do the clip justice, but it is enough for you to get an idea. Before I do an analysis, this reminds me of a great educational activity. In the activity, you give groups of students a full sheet of paper with lines that look something like…

### Error propagation and the distance to the sun

Some time ago, I wrote about the awesome things the Greeks did in astronomy. Basically they calculated the size of the Earth, distance and size of the moon and distance and size of the sun. The value obtained for the distance to the sun was a bit off, but still a bang up job if you ask me. (where bang-up is meant as a good thing) If the greeks were in my introductory physics lab, they would need to include uncertainties with their measurements. What would the uncertainty in the final value look like? In my introductory physics lab course, I have students measure things and estimate the…

### Projectile Motion with a Spreadsheet

Basically, the title says it all. Here is a short tutorial on projectile motion calculations with a spreadsheet. Record your screencast online I left out a lot of details, so maybe these links will help: Spreadsheet tutorial for numerical calculations (video) More details on numerical calculations Projectile motion

### Spreadsheet Tutorial for Numerical Calculations

I really didn't want to post this, but I am going to anyway. I used ScreenToaster.com to make a screen capture movie (with audio) of a tutorial on spreadsheets. This should accompany my previous post on numerical calculations. Free online screen recorder

### Basics: Numerical Calculations

**Pre Reqs:** [Kinematics](http://scienceblogs.com/dotphysics/2008/09/basics-kinematics.php), [Momentum Principle](http://scienceblogs.com/dotphysics/2008/10/basics-forces-and-the-moment…) What are "numerical calculations"? Why are they in the "basics"? I will give you really brief answer and then a more detailed answer. Numerical calculations (also called many other things - like computational physics) takes a problem and breaks into a WHOLE bunch of smaller easier problems. This is great for computers ([or a whole bunch of 8th graders](http://scienceblogs.com/dotphysics/2008/09/…

### Basics: Making graphs with kinematics stuff part II

**pre-reqs**: [kinematics](http://scienceblogs.com/dotphysics/2008/09/basics-kinematics.php) *I don't think you need [part I of this](http://scienceblogs.com/dotphysics/2008/09/basics-making-graphs-with-ki…) if you don't want* So, you still want to make a graph with that kinematics data? You think that graphs on paper are too barbaric? Well, if you are ready, you can use a spreadsheet. But be careful. If you don't know what you are doing, you can cause some damage (much like flying a 747 after reading a blog about it). Spreadsheets allow you to do a couple of things. make pretty graphs…