DP Physics (last assessment 2024)

Question 20N.3.SL.TZ0.4b(ii)

Date	November 2020	Marks available	[Maximum mark: 2]	Reference code	20N.3.SL.TZ0.4b(ii)
Level	SL	Paper	3	Time zone	TZ0
Command term	Explain	Question number	b(ii)	Adapted from	N/A

b(ii).

[Maximum mark: 2]

20N.3.SL.TZ0.4b(ii)

A spaceship is travelling at $0.80 c$ , away from Earth. It launches a probe away from Earth, at $0.50 c$ relative to the spaceship. An observer on the probe measures the length of the probe to be $8.0 m$ .

(b(ii))

Explain which of the lengths is the proper length.

[2]

Markscheme

$8.0 m$ / measurement made on the probe ✓

the measurement made by an observer at rest in the frame of the probe ✓

Examiners report

"In the same frame" does not highlight the need to be "at rest" in that frame, and was the most frequent wrong answer, although a vast majority scored full marks here.

Syllabus sections

Option A: Relativity

Option A: Relativity » Option A: Relativity (Core topics) » A.2 – Lorentz transformations

Option A: Relativity » Option A: Relativity (Core topics)

Question 20N.3.SL.TZ0.4b(ii)

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