The Postulates of Special Relativity and the Loss of Simultaneity · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

Two rules that rebuilt time

Science · Quantum & Modern Physics · ages 18-19
Name ______________________   Date ____________

  1. Which frame counts as inertial?

    • A spinning carousel
    • Steady drift with free particles gliding straight
    • A braking car

  2. Which pair states both postulates?

    • Same laws all frames, same light speed all observers
    • Same time all frames, added light speeds
    • Laws differ per frame, sound fixed

  3. Every observer shares one universal now.

    Circle one:   True   False

  4. Why do the observers disagree?

    • Each finds the other clocks out of sync
    • One clock is broken
    • Light tires on the way

  5. In the train flash, what does the platform see?

    • Both doors lit together
    • Light missing both doors
    • Rear door lit before the front door

  6. Why does fixed light speed forbid everyday addition?

    • Arithmetic is banned on trains
    • Addition would hand light different speeds per frame
    • Light prefers slow frames

  7. A student writes light speed as c plus train speed. What is the error?

    • Light speed stays c for every inertial observer
    • Trains cannot move
    • Addition only works at night

  8. Two split events are simultaneous for riders. What may the platform say?

    • The same order, always fixed
    • That events never happen
    • Either order, simultaneity belongs to frames
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Answer key

For grown-ups. Fold this page away before handing over the rest.

Two rules that rebuilt time W1-mt_kZqVQ18bbc-s1

  1. Steady drift with free particles gliding straight · No push, no spin, and no acceleration means inertial.
  2. Same laws all frames, same light speed all observers · Shared laws plus shared light speed start all of relativity.
  3. False · Simultaneity belongs to each frame, so no shared now exists.
  4. Each finds the other clocks out of sync · Motion scrambles clock sync between frames.
  5. Rear door lit before the front door · The rear door runs into the flash while the front door escapes it.
  6. Addition would hand light different speeds per frame · Adding frame speed to c would break the second postulate.
  7. Light speed stays c for every inertial observer · The second postulate fixes c in all inertial frames.
  8. Either order, simultaneity belongs to frames · Widely split events can even flip order between frames.
Worksheet · LightMySky