Day 6: Translating between graphs, TIPERs, and Light Clocks

Relativity (the class) made the shift from “regular old” relative motion to the beginnings of Special Relativity by thinking about the light clock.

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When we were trying to think about the difference in path length for the light in the stationary clock versus moving clock, one student went up to make the connection to the ball falling on the moving cart from the Frames of Motion video that we saw last class. That discussion also kept emphasizing to us that we needed to specify the frame in order to agree on what we were talking about.

That student was also positing that for the light, it looks like a straight line instead of the parabola we saw in the video because the light moves so quickly. He also wondered whether the light was even affected by gravity at all.

Then we started working through the algebra together as a group to figure out the relationships and the difference in tick length. We got really confused with the concepts and excited about where we are going next.


The Mechanics class is continuing to work on becoming fluent in kinematics graphs, especially on translating between different representations. They took a quick quiz last class, and they are pretty good at being able to describe the motion in words from a velocity graph, but needed more practice with creating the other graphs when they are given one.

We worked through a bunch of TIPERs problems today, and they kept adding additional questions beyond what was asked, making sure that they could also draw a position-time graph or figuring out which additional diagrams would be helpful to their thinking. I think they ended class in a better place. We probably need about one more day of that kind of work, then we can solve some problems, do a practicum, and move on to unbalanced forces.

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