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Date May 2012 Marks available 2 Reference code 12M.3.HL.TZ1.11
Level Higher level Paper Paper 3 Time zone Time zone 1
Command term Calculate, Determine, and Explain Question number 11 Adapted from N/A

Question

This question is about relativistic kinematics.

In a thought experiment, a train is moving at a speed of 0.950c relative to the ground. A pendulum attached to the ceiling of the train is set into oscillation.

An observer T on the train and an observer G on the ground measure the period of oscillation of the pendulum.

Observer G sees a second train moving towards the first train (i.e. towards the left) at a speed of 0.950c with respect to the ground. Calculate the relative speed of the trains.

Markscheme

\(u' = \frac{{ - 0.950{\rm{c}} - 0.950{\rm{c}}}}{{1 - \left( { - 0.950} \right)\left( {0.950{\rm{c}}} \right)}}\);
\(u' =  - 0.999{\rm{c}}\);
Accept calculation with left as positive to give +0.999c.

Examiners report

[N/A]

Syllabus sections

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