Question 19M.3.SL.TZ1.5d.ii
| Date | May 2019 | Marks available | [Maximum mark: 2] | Reference code | 19M.3.SL.TZ1.5d.ii |
| Level | SL | Paper | 3 | Time zone | TZ1 |
| Command term | Determine | Question number | d.ii | Adapted from | N/A |
The diagram shows space and time axes and ct for an observer at rest with respect to a galaxy. A spacecraft moving through the galaxy has space and time axes ′ and ct′.
A rocket is launched towards the right from the spacecraft when it is at the origin of the axes. This is labelled event 1 on the spacetime diagram. Event 2 is an asteroid exploding at = 100 ly and ct = 20 ly.
Using the spacetime diagram, determine which event occurred first for the spacecraft observer, event 1 or event 2.
[2]
line from event 2 parallel to ’ axis intersects ct’ axis at a negative value ✔
event 2 occurred first ✔
Most of the candidates well used the formula for invariant spacetime from the data booklet, but only a few strong candidates were able to determine the time between the events according to the spacecraft observer. This implies a lack of understanding of the concept of invariance for different frames of reference. Most candidates well determined that event 2 occurred first in d ii), with a lesser number showing this correctly via the spacetime diagram.
