Question 18M.3.SL.TZ1.b
| Date | May 2018 | Marks available | [Maximum mark: 3] | Reference code | 18M.3.SL.TZ1.b |
| Level | SL | Paper | 3 | Time zone | TZ1 |
| Command term | Deduce | Question number | b | Adapted from | N/A |
An observer on Earth watches rocket A travel away from Earth at a speed of 0.80c. The spacetime diagram shows the worldline of rocket A in the frame of reference of the Earth observer who is at rest at x = 0.
Another rocket, B, departs from the same location as A but later than A at ct = 1.2 km according to the Earth observer. Rocket B travels at a constant speed of 0.60c in the opposite direction to A according to the Earth observer.
Rocket A and rocket B both emit a flash of light that are received simultaneously by the Earth observer. Rocket A emits the flash of light at a time coordinate ct = 1.8 km according to the Earth observer.
Deduce, showing your working on the spacetime diagram, the value of ct according to the Earth observer at which the rocket B emitted its flash of light.
[3]
line for the flash of light from A correctly drawn
line for the flash of light of B correctly drawn
correct reading taken for time of intersection of flash of light and path of B, ct = 2.4 «km»
Accept values in the range: 2.2 to 2.6.
[3 marks]
