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Galilean Spacetime Diagrans: Instructor's Guide

Main Ideas

Representing motion as worldlines in a spacetime diagram.

Students' Task

Estimated Time: 20 minutes, including wrap-up

Students should be asked to answer the following questions on their whiteboards:
Draw a diagram representing yourself, standing still.
Draw a diagram representing your partner, moving right at 5 mph.
Draw diagrams representing each of you throwing a ball to the right at 10 mph.

Prerequisite Knowledge




  • Ask several students to present/defend their responses.
  • Ask how fast each observer sees each thrown ball move.
  • Ask students to explain how to answer this question from the diagram.
  • Conclude that speed is (reciprocal) slope.

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