Question 19N.3.SL.TZ0.4c(iv)
| Date | November 2019 | Marks available | [Maximum mark: 2] | Reference code | 19N.3.SL.TZ0.4c(iv) |
| Level | SL | Paper | 3 | Time zone | TZ0 |
| Command term | Determine | Question number | c(iv) | Adapted from | N/A |
A train is moving across a bridge with a speed v = 0.40c. Observer A is at rest in the train. Observer B is at rest with respect to the bridge.
The length of the bridge LB according to observer B is 2.0 km.
According to observer B, two lamps at opposite ends of the bridge are turned on simultaneously as observer A crosses the bridge. Event X is the lamp at one end of the bridge turning on. Event Y is the lamp at the other end of the bridge turning on.
Events X and Y are shown on the spacetime diagram. The space and time axes of the reference frame for observer B are and ct. The line labelled ct' is the worldline of observer A.
Determine the time, according to observer A, between X and Y.
[2]
ALTERNATIVE 1
✔
= «–»2.9 × 10–6 «s» ✔
ALTERNATIVE 2
equating spacetime intervals between X and Y
relies on realization that eg:
✔
«s» ✔
ALTERNATIVE 3
use of diagram from answer to 4(c)(ii) (1 small square = 200 m)
counts 4.5 to 5 small squares (allow 900 – 1000 m) between events for A seen on B’s ct axis ✔
«s» ✔
