IB Physics HL A 5 14 Hl World Lines and Speed Questions

Practise IB Physics HL A.5.14 by reading a particle’s speed from its worldline and frame axes on a space-time diagram.

Exam points

Interpret the gradient of a world-line as velocity and identify light-cone limits.
Use world-line diagrams to compare speeds, directions and event relationships using complete evidence.

[Maximum number: 1]

The space-time diagram shows the coordinate axes (x, c t) of an inertial reference frame S. Two events, P and Q, are plotted.

Figure for Question IB Physics HL A 5 14 Hl World Lines and Speed Questions question 1 — IB Physics HL

Events P and Q occur simultaneously in an inertial reference frame $S^{\prime}$ . The clocks of S and $S^{\prime}$ are synchronized at $x=x^{\prime}=0$ .

Determine the speed of $S^{\prime}$ relative to S.

$\left\langle\frac{v}{c}=\frac{1}{3}\right.$ so $\| v=0.33 \mathrm{c}$ or $1.0 \times 10^{8} \mathrm{~m} \mathrm{~s}^{-1}$

Watch for ECF from bi.

Marking guidance:

Allow fraction as the answer, i.e. $\frac{c}{3}$

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IB Physics HL A 5 14 Hl World Lines and Speed Questions question 1