A science museum arranges an experiment to demonstrate the descent of a feather inside a vertical glass vacuum tube. The time taken to fall from rest in the vacuum should be about $0.5\,\text{s}$. Which tube length is needed?
- A$1.2\,\text{m}$
- B$2.5\,\text{m}$
- C$4.9\,\text{m}$
- D$9.8\,\text{m}$