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IB Physics HL A 5 11 Hl Length Contraction Questions

Practise IB Physics HL A.5.11 by identifying proper length, calculating contraction parallel to motion and comparing the measurements of inertial observers.

Syllabus
First assessment 2025
Course
Physics HL
Level
HL

Exam points

  • identify the object’s rest frame and proper length before deciding which measured length is contracted
  • calculate the length parallel to relative motion using L=L₀/γ, with γ from the relative speed and consistent units
  • explain or apply length contraction in a physical scenario by comparing simultaneous endpoint measurements, including tunnel, bridge, star-distance or particle-travel contexts

Learn this topic

Study A.5.11 (HL)—Length contraction conceptsOpen the corresponding Concept lesson for explanations, examples and exam connections.

IB Physics HL A 5 11 Hl Length Contraction Questions question 1

[Maximum number: 2]

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

Later the train is travelling at a speed of 0.60 c . Observer P measures the length of the train to be 125 m . The train enters a tunnel of length 100 m according to observer Q .

Show that the length of the train according to observer Q is 100 m .

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