Category Archives: lab activities

Projectile Motion Lab Practicum and Computational Modeling

In my AP Physics B class, I’m reviewing all of the material on the AP exam even though all of the students studied some of this materials last year in either Physics or Honors Physics. When we do have a review unit, I try to keep it engaging for all students by studying the concepts from a different perspective and performing more sophisticated labs.

When reviewing kinematics, I took the opportunity to introduce computational modeling using VPython and the physutils package. I started with John Burk’s Computational Modeling Introduction and extended it with my experiences at Fermilab where computational modeling plays a role in everything from the optics of interferometers to the distribution of dark matter in the galaxy. I then provided students with a working example of a typical projectile motion model and let them explore. I encouraged them to extend the model to have the projectile launched with an initial vertical displacement.

Later that unit, I introduced the lab practicum which was based on a lab shared by my counterpart at our neighboring high school. The goal of the lab was to characterize the projectile launcher such that when the launcher is placed on a lab table, the projectile will hit a constant velocity buggy driving on the floor, away from the launcher, at the specified location. The location would not be specified until the day of the lab practicum. No procedure was specified and students decided what they needed to measure and how they wanted to measure it. I also used this as practice for writing clear and concise lab procedures like those required on the free response section of the AP exam.

All groups figured out that they needed to determine the velocity of the car (which some had done the previous year) and the initial velocity of the projectile. Some groups used a technique very similar to the previous year’s projectile motion lab where a marble is rolled down a ramp and launched horizontally. These groups fired the projectile horizontally from atop the table and measured the horizontal displacement. Groups that calculated the flight time based on the vertical height were more accurate than those that timed the flight with a stopwatch. Another group fired the projectile straight up, measured the maximum height, and calculated the initial velocity. This group was particularly successful. Another group attempted to use a motion sensor to measure the initial velocity of the ball as they fired it straight up. The motion sensor had trouble picking up the projectile and this group’s data was suspect. A couple of other groups fired the projectile at a variety of angles, timed the flight, and measured the horizontal displacement. Some of these groups later realized that they didn’t really need to perform measurements at a variety of angles. After gathering data and calculating the initial velocity of the projectile as a group, I asked the students to practice calculating their launch angle based on a sample target distance. I hadn’t really thought this lab through and didn’t appreciate how challenging it would be to derive an equation for the launch angle as a function of horizontal displacement when the projectile is launched with an initial vertical displacement. It wasn’t until that night that I appreciated the magnitude of this challenge and then realized how this challenge could be used to dramatically improve the value of this lab.

Most students returned the next day a bit frustrated but with an appreciation of how hard it is to derive this equation. One student, who is concurrently taking AP Physics B and AP Physics C, used the function from his AP Physics C text successfully. Another student amazed me by completing pages of trig and algebra to derive the equation. No one tried to use the range equation in the text, which pleased me greatly (the found candy discussion must have made an impact on them). As we discussed how challenging it was to solve this problem, I dramatically lamented, “if only there was another approach that would allow us to solve this complex scenario‚Ķ” The connection clicked and students realized that they could apply the computational model for projectile motion to this lab. Almost all of the groups chose to use the computational model. One student wrote his own model in Matlab since he was more familiar with that than Python. With assistance, all groups were able to modify the computational model and most were successful in hitting the CV buggy. One group dressed for the occasion:

students ready to launch

Students’ reflections on this lab were very positive. They remarked how they appreciated learning that there are some physics problems that are not easily solved algebraically (they are accustomed to only being given problems that they can solve). They also remarked that, while they didn’t appreciate the value of computational modeling at first, using their computational model in the lab practicum showed them its value. I saw evidence of their appreciation for computational modeling a couple of weeks later when a few of the students tried to model an after-school Physics Club challenge with VPython. For me, I was pleased that an oversight on my part resulted in a much more effective unit than what I had originally planned.

Updated Measurement Uncertainty Activities

Like last year, we started Honors Physics with Measurement Uncertainty activities. Based on last year’s experience, last fall’s Illinois Science Education Conference, and this summer’s QuarkNet workshop “Beyond Human Error,” we made some minor modifications.

With the popularity of the LHC’s five sigma result, there was more of a context in which to introduce the concept of measurement uncertainty. I mentioned how calculus and Monte Carlo techniques could be used, but we stuck with the Crank-Three-Times method for this algebra-based class.

What was really missing in last year’s activities was how to estimate the measurement uncertainty when performing computer-based experiments. There are so many factors that contribute much more significantly to the measurement uncertainty than the computer-based measurement devices. David Bonner presented on “Learning Physics Through Experiments: Significance of Students’ Interpretation of Error” at the Illinois Science Education Conference last fall. One great idea I took away from his session was a simple and effective approach to addressing this challenge where students perform many trials to establish a range of values from which the measurement uncertainty is determined.

We rewrote the fifth station to introduce students to this method. Rather than using stopwatches, we setup two daisy-chained photo gates connected to a LabQuest 2 to measurement the elapsed time as a cart travels from the first gate to the second. The uncertainty of the LabQuest 2 is insignificant compared to other factors that affect the motion of the cart. Students performed ten trials and determined the measurement uncertainty from the range of values that they measured. We will use this technique throughout the year to estimate the measurement uncertainty.

Download (PDF, 35KB)

Holography Resources

This post is primarily for those teachers attending the Summer 2012 QuarkNet Workshop at Fermilab. However, other teachers interested in making holograms may find it useful; if you have questions, please contact me as you won’t have the experience of making your own hologram during the workshop.

Teachers at my school and, most recently, myself have learned how to make holograms in the classroom from Dr. Tung H. Jeong, a recipient of the Robert Millikan Medal from the American Association of Physics Teachers for his work in holography. After attending an AAPT workshop led by Dr. Jeong, I refined our techniques for making holograms and we started making transmission holograms in addition to reflection holograms.

When introducing holography to students, I start with a video from the How It’s Made TV show about holography.

I then introduce the holography and advise students how to select objects from which to make a hologram. The slides I use are below.

Download (PDF, 810KB)

We order all of our supplies from Integraf, which is associated with Dr. Jeong. Integraf has several tutorials on their web site which are essential reading:

  • Simple Holography should be read first. It describes all of the basics of making reflection holograms with many aspects applicable to transmission holograms as well.
  • How to Make Transmission Holograms. I prefer to make transmission holograms as they have several advantages over reflection holograms. The only disadvantage is that they require laser light to view. However, given how affordable laser pointers (green are best) have become, this disadvantage is becoming less significant.
  • Instructions for JD-4 Processing Kit. I believe this PDF file is the most recent version of the instructions. Similar directions are on the website, but the timings in this document are slightly different.

Supplies

  • PFG-03M Holographic Plates (2.5″ x 2.5″, 30 plates, $105, Item #S3P-06330)
  • JD-4 Processing Kit ($17, Item #JD4)
  • Holography Diode Laser (650nm (red), 4mW, $36, Item #DL-4B)

A previous post on holography describes how I setup a station and has several pictures.

Reflection and Refraction Activities

We are currently in the midst of the geometric optics unit in my honors physics class and just finished waves, which includes reflection and refraction, in my regular physics class.

My colleagues and I have developed a series of reflection and refraction activities that provide a shared experience that can be leveraged as we explore reflection and refraction of light. In addition, students find these activities engaging and they generate a lot of great questions.

I hope you find a new activity that you can use in class.

Here are the handouts.

Download (PDF, 41KB)

Download (PDF, 38KB)

I don’t have photos of the reflection activities, but I think they are pretty self explanatory. If not, ask, and I’ll clarify.

I do have photos of the refraction activities. I need to give credit for the first activity which is a recreation of an AAPT Photo Content winner from a few years ago.

Colored paper behind glasses

Colored Paper behind Water Glasses

Pencil in air oil water

Pencil in Air, Oil, and Water

Toy car in beaker 1

Toy Car in Round Beaker

Masses Hiding in Fish Tank (Total Internal Reflection)

Resources for Middle School Science Activities

When I visited National Instruments and shared my experiences with STEM in high school, a talked to a few friends who were involved in various types of science programs for middle school youth. They were interested in activities they could use to help develop fundamental scientific understandings (such as scale) as well as be engaging and provide an opportunity to learn about various phenomena. I don’t have any experience at the middle school level, but I reviewed the various projects that I’ve done (or hope to do) with high school students either in class or as part of Physics Club.

If you have a few favorite activities that would be appropriate for these students, please leave a comment. I’ll pass along a link to this post to my friends back in Austin.

Science and Engineering Projects

Scale

Citizen Science

Great resources:

N3L Activity Stations

While the Newton’s 1st Law activities serve as a fun and short introduction, the Newton’s 3rd Law activities provide a shared experience that spans several classes. The activities that the students explore are selected to highlight the most common preconceptions that students have about Newton’s 3rd Law. I stress how important free-body diagrams are as a tool in their physics toolbox and that, once they are adept at drawing free-body diagrams and once they actually trust their free-body diagrams, they will be able to explain a number of counter-intuitive situations. I introduce these activities by stating that Newton’s 3rd Law is one of the most easily recited laws of physics and yet is least understood. Here are the activities:

Download (PDF, 35KB)

Sequential Spring Scales

Sequential Spring Scales

The spring scales are initially hidden under the coffee filters. Only after students make their prediction are the coffee filters removed. Most students do not predict that the spring scales will read 10 N. Some predict 5 N (the spring scales split the weight). Some predict 20 N (10 N each way adds up to 20 N). In addition to drawing the free-body diagrams, this scenario can be explored further by asking students to predict the reading on the scales if one of the weights is removed and the string is tied to a clamp instead.

Bathroom Scale

This station provides an important shared experience that we will refer back to when discussing the elevator problems later in the unit. This station also generates a number of excellent questions such as “would the scale work on the moon?” and “how could you measure mass on unknown planet?”

Twist on Tug-of-War

tug-of-war

Students were very interested in this station this year since they were in the midst of Homecoming Week and inter-class tug-of-war competitions were being held. It may have been the first time free-body diagrams were used in the planning of the tug-of-war team’s strategy. The dynamics platform in the photo is a cart build from plywood and 2x4s with rollerblade wheels and has little friction. Most students claim that whoever wins the tug-of-war pulls harder on the rope than the person who loses. Only after drawing the free-body-digram and trusting it, do they realize this is not the case.

Medicine Ball Propulsion

Medicine Ball Propulsion

This is a fairly straight-forward station. I often wander by and ask the students exploring it why they don’t move backwards when playing catch under normal situations. I also check at this point and see if they are convinced that the force on the ball by them is equal to the force on them by the ball.

Computerized Force Comparison

This is the most important station in that it helps students truly appreciate Newton’s Third Law. I setup several of these stations to make sure that everyone has an opportunity to watch the graph in real-time as they pull on the force sensors. This is the standard Modeling activity for Newton’s 3rd Law. For students still struggling to accept Newton’s 3rd Law while working through this activity, I challenge them to find a way to pull on the two sensors such that the forces are not equal in magnitude and opposite in direction. This activity also counters the misconception promoted by some textbooks (perhaps unintentionally) that the “reaction” force follows the “action” force. Students can clearly see that both forces occur at the same time. (We refer to paired forces according to Newton’s 3rd Law, not action-reaction forces.)

WALL-E and the Fire Extinguisher

Who doesn’t love WALL-E? I repeatedly loop through a clip from the WALL-E trailer. In addition to the questions on the handout, I ask students what is incorrect about the physics in the scene. This year, I also showed students this clip that Physics Club filmed several weeks ago:

N1L Activity Stations

I like to introduce Newton’s First Law with a series of activity stations for students to explore followed by a couple of demos. They have fun and it provides shared experiences which we can refer back to later. Here is the activity sheet that guides them:

Download (PDF, 32KB)

Many of these stations and demos have as much to do with impulse as they do with Newton’s First Law. I mention this and we revisit these stations and demos later when studying impulse.

Most of these stations and demos are fairly self explanatory. However, a few can benefit from a photo. Here is the “Nuts about Hoops & Bottles” station:

nuts, hoop, bottle

You quickly grab the hoop with a fast, horizontal motion. This station can become overcrowded because some students obsess over trying to capture the most nuts in the bottle. (I’ve seen students catch over twenty.)

The “Hitting the Stake” station is perhaps the most surprising to students. It is easy to build and looks like this:

hitting the stake

The “Spin the Human” station works best on teachers with little hair. We have one constructed from pool balls. This one is built with golf balls and a coat hanger:

spin the human

It is best to put the “Chopping Blocks” station in the corner. Some students have an incredible amount of aggression to release.

I’m sure everyone has seen the “Clearing the Table” demo. If not, MythBusters has an extreme version.

A couple of years ago, I captured the “Egg Drop Soup” demo with the high-speed camera. I usually have all four eggs make it.

What is interesting about these activities is the evolution of this lesson. When I started teaching, these were all demos. I put on the show and the students’ engagement was that they laughed. A few years ago, my team transitioned these from demos to activities. More fun, more engaging. Based on a suggestion from my instructional coordinator, I now introduce each station and have the students record their predictions before get up and start visiting stations. This ensures they actually make predictions since many of these stations are too enticing for them to make predictions before playing with them.

Maybe I’ll let students “Clear the Table” next year.