Ellen is an observer on a spaceship in deep space. Outside her window she can see two small asteroids that are stationary relative to
her spaceship, and are both on her x-axis. The closest asteroid is 1.80 × 107 km away, while the second is 3.30 × 107 km away. Ellen
observes signal lights on both asteroids appear at the same time, which she notes to be 0 seconds on her clock. She sees both signal
lights turn off 56.0 s later.
On the spacetime diagram below Ellen’s reference frame is represented by the x and t axes.
River sees the same events from her spaceship, which is travelling at a speed of v relative to Ellen’s spaceship. Her reference frame is
represented by the x’ and t’ axes on the spacetime diagram below. The divisions on River’s axes are spaced the same as Ellen’s.
Critically analyse the information to compare how the events on the two asteroids appear to Ellen and River. In your answer you
must include the following information
 A completed spacetime diagram showing the events on the two asteroids. You can copy the axes below into your document
to complete your diagram.
 Determine the relative velocities, v of the two spaceships.
You must choose which other values and information to present in your answer. In your answer you should explain how you
determined the information presented.
Question 2 Marking Rubric
A grade (8) B grade (6-7) C grade (4-5) D grade (2-3) E grade (0-1)
Critically analyses predictions
of special relativity to create
insightful solutions, with
evidence, to the given
problem.
Analyses predictions of
special relativity to create
solutions, with evidence, to
the given problem.
Explains predictions of
special relativity that
relate to the given
problem.
Describes
predictions of
special relativity
that relate to the
given problem.
Identifies
predictions of
special
relativity that
relate to the
given problem.
x (×10^6 km)
t (×c m)