Final answer:
In a universe where the speed of light is only 100 m/s, an airplane flying at 300 km/h would appear nearly its proper length of 40 meters to an observer at rest, as relativistic effects would be negligible at that speed.
Step-by-step explanation:
The question is asking about how the length of an airplane would be affected by relativistic effects if the airplane is travelling in a universe where the speed of light is only 100 meters per second (m/s). Relativistic length contraction occurs when an object moves at a significant fraction of the speed of light, according to Einstein's theory of special relativity. However, in the given scenario, the airplane is flying at 300 kilometers per hour (km/h), which is approximately 83.33 m/s. Since this speed is much less than the hypothetical speed of light in this universe (100 m/s), relativistic effects would be negligible, and thus the airplane would appear to be essentially its proper length of 40 meters to an observer at rest.