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Question 19M.3.SL.TZ1.5d.i

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Date May 2019 Marks available [Maximum mark: 2] Reference code 19M.3.SL.TZ1.5d.i
Level SL Paper 3 Time zone TZ1
Command term Determine Question number d.i Adapted from N/A
d.i.
[Maximum mark: 2]
19M.3.SL.TZ1.5d.i

The diagram shows space and time axes  x and ct for an observer at rest with respect to a galaxy. A spacecraft moving through the galaxy has space and time axes x ′ and ct′.

A rocket is launched towards the right from the spacecraft when it is at the origin of the axes. This is labelled event 1 on the spacetime diagram. Event 2 is an asteroid exploding at  x = 100 ly and ct = 20 ly.

(d.i)

An observer in the spacecraft measures that events 1 and 2 are a distance of 120 ly apart. Determine, according to the spacecraft observer, the time between events 1 and 2.

[2]

Markscheme

9600 = 1202 − c2t2 ✔

ct = «−» 69.3 «ly» / t = «−» 69.3 «y» ✔

Allow approach with Lorentz transformation.

Examiners report

Most of the candidates well used the formula for invariant spacetime from the data booklet, but only a few strong candidates were able to determine the time between the events according to the spacecraft observer. This implies a lack of understanding of the concept of invariance for different frames of reference. 

Syllabus sections