Welcome to the 8th Annual Physics Day at Great America! We are expecting a beautiful, sunny day with a high in the low 70′s – a perfect day to do some amusement park physics. Here are some logistics to consider for the day
- Got the 911? Meet after G period in the athletic parking lot, next to the vans. We will leave by 9:15 am
- Got equipment? Be sure and bring all the necessary equipment to do the physics
- Got sunscreen? It looks to be sunny, and maybe warm, so dress appropriately.
- Got extra cash? Each student is responsible for his/her own food at the park.
- Got Lab Prep? My goodness, please make sure you have planned your lab beforehand
- Got background? Make sure you read the packet so you know all the background
- Got the fun? Yup, I want you to do well but I want you to have fun doing physics
I will give you all my cell phone number once we get to the park so you can reach me if there are problems. I am looking forward to tons of fun!
MrQ
The GA Crew
The day after: so how did it go? There were certainly some bumps in the trip. The main issue we faced was the weather, and by “weather” I mean the whole gamut of conditions were present. Rain? It dumped for a while. Sunshine? Sure, we had some of that. Cold? You bet, as it alternated between comfortable and freezing at times. It certainly leaves us with stories to tell about hiding from the rain or riding in the rain. It also had the benefit of keeping all crowds away.
The real unfortunate consequence of the rain is that it closed more rides than normal. Before entering the park I made the decision to hand out my cell phone number so that the students could reach me. As it turned out it was a good decision as I was able to help many students on the fly. I will look for more ways to incorporate that into the future.
I had a blast riding rides with students and spending time with a faculty buddy while there. I find it interesting that a day like this allows for relaxation but accomplishes so much in terms of working through ideas that don’t otherwise get discussed. It also allowed me to talk with students out side of the classroom context. It is possible that I am robot on most days and so maybe this adding a human quality to their experience.
Lab Report Assignment Notes
Here are some things to keep in mind about the lab report when writing this. A lab report is like an essay that could be written in English or History class. It has a different structure, obviously, but it should read as a continuous story. Students should focus on how the parts connect with the others. The handouts and the rubric all try and help convey this to you as well.
Specific Reminders
- Submit your reports to Turnitin.com by the due date as well (one per group)
- Send your photos to me via email
GLX
The upcoming amusement park trip is the perfect opportunity to try out the digital data collection devices current owned by the school. While I have been reluctant to have students take these to the park in the past (mostly because I am nervous about lending these materials!), I am ready to experiment more this year. So what are we talking about here?
To start, the students in this course have been well-trained on the use of data collection devices. Specifically, they have used the “Xplorer GLX” model made by Pasco Scientific. While they don’t have the slick interface that some many devices have now (think: iPhone), they have all of the capabilities needed to change classroom laboratories into relevant experiences, modeling those needed for true science education. The model has two basic parts: the GLX and the sensors. First, the device itself (GLX) is a very versatile machine and can interpret information from any of the sensors that connect to its data ports. The sensors can measure any number of quantities: force, distance, voltage, temperature are examples of this. With the data displayed on the screen in numeric or graphic forms, the students have different options for accessing the meaning of the data.
In thinking about the amusement park assignment there are a few ways in which this could be deployed. The sensor that might be the most useful is the motion sensor. It can display a distance as well as velocity and acceleration quickly and readily on the screen. For students wishing to get a read on these quantities this might be the easiest way. The one caveat is that it has a very limited range and any motion that is more than a couple of meters away would not be read at all. Still, within this distance it might be much easier than trying another method.
The next sensor that could be deployed is the acceleration sensor, which tracks acceleration in the x, y, and z planes as it moves. While this might have been the best way to get this information 10 years ago, they are almost a footnote given that the iPhone has one built into the hardware. Now all a student has to do is download an app that does the same thing.
Other sensors? I will have to ask my students what they think – are any of the other sensors potentially useful in this assignment?
Coaster
I’ve been thinking about the challenge of making measurements at the amusement park. Specifically, many of the assigned problems require an application of kinetic energy (KE = 1/2 mv2), gravitational potential energy (GPE = mgh) and work (W = Fd). The interchange between the three is easy to grasp and the students have practiced this many time in this course. Train at the top of the hill loses GPE and acquires KE, with the exception of the work done by friction.
But how do I measure speed, necessary to calculate KE? Well, there is an easy trick that helps with this and the measurements are very easy to make. Think about distance: how do I access this? Well, think about how easy it is to measure the length of the train. Each is composed of multiple cars that come to a stop while loading and unloading. If I make a quick measurement of the length of a section of the train and then count the number of cars I can find the total length of the train, probably to within 10% of the true length.
In order to find velocity (or speed), what remains is time and every student carries a timer built into a phone device. If I wish to know the velocity at the top of the hill then all I need is to time how long it take for the car to pass a certain point at the top. If I wish to find the speed at the bottom then I choose another location and do the same. Repeating the measurement increases the chances that the measurement will be valid.
Now, what about other distances? If I know the length of a train and I examine (from afar) what percentage of a length of track (or loop) the train occupies then I can reasonably estimate the distance of something that I could never reach.
One final word about mass. What should I do if I get stuck on the mass of a car or train? The easiest was is to assume 1 kg (yes, just 1 kg!) for the problem. Therefore any answer you get would be per kilogram by default. That way any futre research would just multiply the factor found.
Log Ride
Objective: Determine the average stopping force of the water on a log in the water ride as it comes to a stop after the ride down the chute.
Approach: We clearly need a handle on the core physics of the problem. What are the major concepts? It seems as though this might revolve around the idea of energy and energy conservation (or lack thereof). Consider the log at the top of the ride: it has a constant speed and is about to shoot down the long slide ramp. At the bottom of the ramp it has a greatly increased speed, having increased its velocity with almost no friction. So we have: top = low KE and bottom = higher KE. The sudden slowing at the bottom occurs over a very short distance. Over this short distance almost all of the KE is taken away by the water. Kinetic energy becomes work and since work = force times distance, simply measuring the distance will allow you to calculate the force applied. The tricky part might actually be to determine the velocity of the log at the bottom of the ride. Yet by measuring time and distance near the bottom this, too, can be easily tackled.
Geometry
With the trip to the amusement park only days away, it is prudent to examine how a student might begin to make appropriate measurements. The use of accelerometers while at the amusement park adds to the experience and the enjoyment of students in several ways. It gives the students a direct way to check any calculated values for accelerations and “g” forces that they have made as well as providing an opportunity for students with less sophisticated math backgrounds to quantitatively study the rides. It also provides a creative, hands-on activity for the classroom where students can design, construct and test the devices to be used at the amusement park. Trying to foresee and provide for all of the contingencies to be encountered at the park can lead to several days of class discussion and problem solving sessions.
There are basically two types of accelerometers, vertical and horizontal. Both directions are relative to the seat the rider sits in on the ride, with vertical taken as perpendicular to the seat.
Horizontal Accelerometer: this can be used to measure heights and accelerations by recording only the angle from the vertical.
FBD
- Materials: plastic protractor, string, small rubber stopper with hole, large plastic drinking straw masking tape.
- Calibrating: When holding this device so that the straw is horizontal to the ground, there are two forces acting on the rubber stopper. Gravity and the tension in the string. T can be resolved into its x and y components. The string supplies the force necessary to accelerate the stopper to the left or to the right. The stopper is accelerating in the horizontal direction only.
- Measuring Heights: One of the nice features of the horizontal accelerometer is its double use as a clinometer. By sighting the top of the object through the drinking straw, the angle of inclination can be determined from the protractor by subtracting 90 from the angle indicated by the string. Depending on which base line the student is able to measure, the height of object can be found by using the appropriate formula.
Estimating Distances: how in the world can I estimate the distance?
Estimating distance is not as difficult as it might seem. Basic students might be terrified when told that they don’t have access to a meter stick, tape measure or other device which produces hard numbers. Since students don’t have access to the rides themselves, what are they to do? I think the key is repeating structures of the rides themselves. All that’s really needs to be measured is the length of a single unit of the ride that repeats along the ride. This can be done with measured pacing (knowing one’s own stride and repeating the walk).
Now what do I do?
The final key can be found in the preparation before the field trip. Almost everything can be boiled down to a combination of length and time, with a little help from mass and acceleration estimation. Knowing how to boil down each question into the subsequent parts will transform a hairy problem into a very accessible… well… bald one I guess.
