Physics HL · Chapter 6: Relativity
Chapter 6 Wrap-Up
Consolidate a practical solving routine for relativity problems across equations and diagrams.
Estimated time: 7 minutes
A Reliable Problem-Solving Sequence
Start every problem by naming the frame in which each quantity is measured. Next, mark whether a given interval is proper time or proper length. Then choose the matching relation: Lorentz transformations for event coordinates, dilation or contraction formulas for special intervals, velocity addition for moving-signal questions, and spacetime diagrams when causal or simultaneity interpretation is central.
Check answers against limiting behavior. As v approaches zero, your result should approach the Galilean approximation. As v gets close to c, gamma should grow and corrections should become prominent. For any speed-composition question, ensure final speed remains below c for matter.
Key Takeaways
- Einstein's postulates require Lorentz, not Galilean, transformations at high speed.
- Space and time coordinates are frame-dependent; spacetime interval is invariant.
- Proper time dilates by gamma in frames where the clock moves.
- Only lengths parallel to motion contract, and simultaneity conditions matter.
- Relativistic velocity addition preserves c as a universal upper limit.
- Spacetime diagrams unify equations, simultaneity, and causality in one visual model.