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Question 20N.3.SL.TZ0.b(i)

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Date November 2020 Marks available [Maximum mark: 2] Reference code 20N.3.SL.TZ0.b(i)
Level SL Paper 3 Time zone TZ0
Command term Plot Question number b(i) Adapted from N/A
b(i).
[Maximum mark: 2]
20N.3.SL.TZ0.b(i)

The spacetime diagram is in the reference frame of an observer O on Earth. Observer O and spaceship A are at the origin of the spacetime diagram when time t=t'=0. The worldline for spaceship A is shown.

 

Event E is the emission of a flash of light. Observer O sees light from the flash when t=9 years and calculates that event E is 4 ly away, in the positive x direction.

Plot the event E on the spacetime diagram and label it E.

[2]

Markscheme

X value of E at 4 «ly» ✓

Y value of E at 5 «y» ✓

Examiners report

Event E is the event when the light is emitted (4,5). Some candidates missed that and placed it at (4,9).

To determine these coordinates candidates were expected to construct a light path from (0,9) which intercepts at x=4 and t=5. This is a very common mistake which needs careful explanation by teachers.

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