IB Physics HL A 5 12 Hl Relativity of Simultaneity Questions

Practise IB Physics HL A.5.12 by identifying simultaneous events and determining their order for observers in different inertial frames.

Exam points

Explain the relativity of simultaneity for events separated in space.
Use Lorentz transformations to determine whether events are simultaneous in different inertial frames using complete evidence.

[Maximum number: 3]

An observer P sitting in a train moving at a speed v measures that his journey takes a time $\Delta t_{\mathrm{p}}$ . An observer Q at rest with respect to the ground measures that the journey takes a time $\Delta t_{\mathrm{Q}}$ .

According to Q there is an instant at which the train is completely within the tunnel. At that instant two lights at the front and the back of the train are turned on simultaneously according to Q .

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The spacetime diagram according to observer Q shows event B (back light turns on) and event F (front light turns on).

Deduce, using the spacetime diagram, which light was turned on first according to observer P.

lines parallel to the $x^{\prime}$ axis and passing through B and F;
intersections on the $ct^{\prime}$ axis at $\mathrm B^{\prime}$ and $\mathrm F^{\prime}$ ;
light at the front of the train must have been turned on first

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IB Physics HL A 5 12 Hl Relativity of Simultaneity Questions question 1