A Call for Myths!

Physics students will soon be working on a "MythBusters" project modeled after the show MythBusters. Mythbusters is a science show that airs on the Discovery Channel on Wednesdays from 9 – 10 PM (and re-runs can be found on the Discovery Channel throughout the week). Each hour-long episode features 3 – 4 science myths or questions that are put to the test. The show’s hosts introduce the myth, design an experiment, perform the experiment, and then analyze the data to label the myth as “busted,” “plausible,” or “confirmed.”

In our project, students will carry out an experiment to test their own myths. Perhaps the hardest part of this assignment is coming up with a good myth to test. Myths can range for commonly-repeated statements such as "you can't fold a piece of paper in half more than 7 times" to cartoon physics such as "banana peels are really slippery" manufactures' claims about their products.

For those interested, details about the project can be found in the handout.

In the comments section, I'd like to know what myths you've heard about and would like to suggest to be tested. If possible, I'd like to avoid having any groups test a myth that has been featured on MythBusters. Post away!

Equilibrium Software

Photo by Felipe Gabaldon

Calculating individual forces within systems in equilibrium can be a daunting task! As we've seen in class, the process involves drawing a free-body diagram, resolving forces into components, and writing equations for each dimension. Almost always, this process leads to solving a system of equations. Depending on the particular problem, this system of equations can be quite difficult.

Computers are well-suited to doing tedious calculations. They certainly have the ability to solve the system of equations mentioned above. Do a little searching online.

1. What are some software programs/packages that engineers use to solve problems of static equilibrium?
2. Are there any freeware programs that can solve statics problems?
3. Can you find any applets online that allow a user to manipulate beams, cables, masses, etc., and will then display the resulting force in a particular piece of the structure?

Share your links in the comments.

The Sliding Glider Problem

Photo by wwarby

In class, we did an experiment where we calculated the acceleration of a glider down a 2.81° incline under ideal conditions. We followed this up by using the computer tools to measure the actual acceleration. Can the acceleration of the glider be determined without a computer?


I recorded a video of the experiment:

Our air track is exactly 2 meter  long. Since there are bumpers at the ends of the track and the glider itself is 13 cm long, the total distance traveled is slightly less than 2 meters. It's a little hard to see in the video, but the front of the glider is at the 20-cm (or .20-m) mark on the air track. The audible click occurs when the front of the glider reaches a position of 2.00 m.

1. How far does the glider travel as it slides down the ramp in this experiment?
2. How long does the trip take? (HINT: use a stopwatch while viewing the video or, depending on your browser or software, use the video's time code.)
3. The glider starts from rest and accelerates constantly during its trip. What is the value of this acceleration?

If you do these calculations, please briefly explain how you are getting your results. How does our "hand" calculated value for the glider's acceleration compare to both the theoretical value and the computer-measured value?

Dueling Ramps

Consider the two frictionless ramps shown in the above sketch. Identical gliders are positioned so that their center of masses are both 10 meters above the ground. Answer as many of these questions as you can... ...

1. What is the acceleration of the glider on the left ramp?
2. What is the acceleration of the glider on the right ramp?
3. How fast is the glider on the left moving when it reaches the ground?
4. How fast is the glider on the right moving when it reaches the ground?
5. Which glider reaches the ground first *and why*?

Vector Components

Using vector components proves very useful in physics. Many problems can be solved by resolving vectors into components. Without components, these same problems are very challenging! Head over to Zona Land Education and play around with their component visualizer. Within the applet, there are 4 "styles" from which to choose. Which style seems the most intuitive to you? When you imagine a vector's components, which style do you mentally picture?

Vector components allows us to easily add non-perpendicular vectors together. Even though this is not a difficult task, it is rather tedious. Many graphing calculators can add vectors, but the vectors are usually not in the same format that physics students are used to seeing.

Do an internet search and see if you can find any free, online vector calculators that can add two vectors together, and post a link to your favorite as a comment.