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## NetLogo User Community Models

WHAT IS IT?

This model represents Newtonian Relativity (or Classical Relativity) with a car traveling on top of a traveling railroad flatcar.

HOW IT WORKS

Both the car and the railroad flatcar travel at a set, fixed speed. The speed of the car is set so that it will travel from one end of the flatcar to the other, while the flatcar travels across the speed.

There are three options to set:
1. Set show-markers to Off (do not show any markers) or On (show makers for the flatcar and the car, the vectors showing each of the distances traveled, and the numerical values).
2. Set the speed of the flatcar in arbitrary units, from .05 to .2 . The speed of the car is set to a multiple of this speed.
3. Run the model in reverse.

Set 1 and 2 before Setup, because they have no effect after Setup. You can flip back and forth between forward and reverse while the model is running.

HOW TO USE IT

Set the switches and sliders as in 1 and 2 above, then click Setup, and then Go.

THINGS TO NOTICE

The distance from the station (left-hand edge of screen) to the rear of the flatcar, plus the distance from the rear of the flatcar to the rear of the car, is equal to the distance from the station to the rear of the car. This is the premise of Newtonian Relativity.

NOTE: Because of rounding errors, the distances will sometimes not add up exatly.

THINGS TO TRY

A first run with show-markers set to Off will illustrate the basic situation, with the car traveling on top of the traveling flatcar. Then set the markers to On to see the distances.

EXTENDING THE MODEL

The model could be extended to show time dilation and space compression at relativistic speeds.

NETLOGO FEATURES

This model uses the new "box" world, where the coordinates do nor wrap around. In the normal torus world, the distance markers flip to the right-hand side as soon as the flatcar reaches the midpoint.

RELATED MODELS

I do not know of other models related to this one.

CREDITS AND REFERENCES

Wilensky, U. (1999). NetLogo. http://ccl.northwestern.edu/netlogo/. Center for Connected Learning and Computer-Based Modeling, Northwestern University, Evanston, IL.