Q3 · 2025 · Paper 2Simple familiar5 marks
QUESTION 3 (5 marks)
A spaceship travels at a velocity of towards a distant planet. The spaceship sends a light beam signal to the planet.
a)[2 marks]
Draw a conclusion about the speed of the signal as seen by observers on the planet. Justify your response.
b)[3 marks]
Observers on the spaceship measure the spaceship’s length as 35 m.
Calculate the length of the spaceship as seen by observers on the planet. Show your working.
WORKED SOLUTION
5 marksQCAA guide · typeset solution
ANSWER
See worked solution below.
Worked solution
a) The second postulate of special relativity states that the speed of light in a vacuum has the same value in all inertial frames of reference. Thus the speed of the signal will be .
b)
Length of spaceship =
recognises that the speed of light is the same in all inertial frames of reference
concludes speed of signal is equal to
recognises that the scenario relates to length contraction
provides appropriate mathematical reasoning
calculates the relative length
One QCAA sample method typeset for web; criterion wording is adapted from the official marking guide.
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