I REALLY need some creative help-please!-job at stake!!!

[two_sets_of_twins]

Hi everyone,
I'm a 3rd grade science teacher, and for our science fair we have to build a model of a roller coaster for school...(centrivical force project). I have NO IDEA WHERE TO START and my boss has been asking me on a daily basis where my supplies are and when I'm going to start it. This is something I'm going to have to do in class along with my students, I dont have a creative bone in my body when it comes to making models...How do I make a model rollercoaster out of simple items I can get in school? or around the house? or at a stationary store? because we're not allowed to purchase any models, we have to make them, and it has to be something 3rd graders can do too! Now you see why I'm stuck!!?? I guess we could use some sort of tubing or cardboard and what would I use for the seats or the tracks? and it has to have a loop in it! I've been surfing the net for a week and can't find anything to help me, that's why I posted here!
I've only been working in this school for 2 months and I'm REALLY trying to prove myself to my boss...Please....PLEASE someone if you have ANY suggestions or ideas you have NO CLUE how much it'll be appriciated. Thanks for your time.

[deleted-2574]

Hi two_sets_of_twins!

Some thoughts:

- for the tracks you can product like K'nex, my kids had them.
- for the design typing "rolling coaster design" into google yields a lot of papers with the basic principles of roller coasters
- typing "rolling coaster design software" into google yields software that will help in design of a roller coaster. I don't know if any of these will be necessary using the thoughts in the papers.

I don't know if this helps. Please let me know.

[deleted-2574]

Hi two_sets_of_twins!

I forgot to add in my last message that an idea for the seats in the roller coaster is use egg crates.

I credit my wife for much of the above, K'nex, egg crates and some of the wording in google searches.

[deleted-71254]

How primative does this have to be? Frankly, I'll bet that half of your third grade kids have the best materials sitting at home already, the male half! Most boys that age love the Hot Wheelsâ„¢ toy cars and have track for them. These included a loop.

I'm an engineer... and I can't image building anything from scratch, with the help of third graders that would have the reduced friction to get enough speed to demonstrate a loop fast enough to hold an object to the car, or the car to the track, during a loop.

BTW, please don't teach the incorrect concept of "centrifical force". There is no such force. The correct analysis of a roller coaster loop is that the turn in the loop applies a physical constraint (mediated by the electrical force of electrons in the atoms of the track) pushing the car in a new direction moment by moment, when, by inertia (Newton's laws of motion), it would much rather continue in a straight line. This constant centripidally oriented turning force may feel like it is acting in the other direction, but it is an illusion. (Think of a person inside of a rocketship in space as it is accellerated, the person inside "feels" a force pushing her to the "floor", but it is in fact the "floor" that is pushing her.)

The way to demonstrate this effect is to have an object on a string, swung around. When the string is released, it does NOT fly directly away from the center, instead, it flies in a straight line tangent to the circle, that is to say, that it continues in the direction in which it was travelling the instant it was released.

So, if there is no such force as "centrifical"... how does the car stay on the track at the top of the loop? Because the centripedally oriented turning is accellerating the car faster than gravity would have. (Think of an object in your hand as you throw it downwards, if you push it faster than gravity would have accellerated it, it feels like it is "pushing back" on your hand. Does that mean that there is an upwardly acting "force"? No.)

When incorrect physics are taught in elementary school, and even high schools, colleges and universities have to spend time unteaching things first ! (This is one of my pet peeves about science education.)

[deleted-71487]

The Hot Wheels idea is a reasonable one. You could also build a superstructure out of popsicle sticks and use something like k'nex or even model train tracks for guiding the cars.

I feel compelled to mention, however, that there are 2 kinds of centrifugal "force", reactive and fictitious.

First, reactive centrifugal force (the force Newton's laws tell us is exerted upon the object providing the centripetal force in equal and opposite measure): It is a real force in every sense of the word. It just doesn't work in the intuitively obvious manner.

The fictitious centrifugal force "felt" by the object being accelerated isn't a real force, but mathematically it can still be a useful concept it you are trying to analyze dynamics inside a rotating frame of reference.

"Coriolis force" is another fictitious force that doesn't really exist (it's a side-effect of the earth's rotating frame of reference), but it is nonetheless an extremely useful concept when attempting to perform weather prediction.

For a very good discussion of this, see: http://en.wikipedia.org/wiki/Centrifugal_force

[Greist_Physics]

Hi, I'm a new member to this community, and a High School Physics teacher. In my classes, the students are in the process of completing roller coaster models that are designed to take a marble through a bunch of loops and turns. At the third grade level, I don't think your students would be expected to do anything more complicated than a group of high school seniors!

A very simple solution: Build a roller coaster track for a marble to demonstrate loops, turns, energy, etc. A very nice material to use is foam pipe insulation. All you have to do is cut it in half. It is extremely easy to shape into loops, hills... whatever you want. Also, at about $3 or $4 for 12 feet, it's VERY affordable! You can get it at Home Depot in any size you would need. Get a few and experiment for the best!

As far as supporting it, I would suggest wooden dowels, popsicle sticks... whatever you have available.

Let me know if you try this. If so, I may be able to offer more construction tips. Good Luck!

[deleted-71360]

This is crazy!

I think your boss is expecting too much for third graders to understand.

My son is in the middle of his teacher training for grade school level, and he reports that none of the teacher qualifications testing required physics to the degree you are requesting help on.

I like the foam pipe insulation idea. It is simple and straight forward. Be aware that the marble may have high rolling friction due to the soft nature of the foam material.

Robert Reavis