You want to park your 20 feet long super-souped-up 1971 Cadilac inside a barn that is only 10 feet long. How fast do you need to drive it to fit it in just snuggly?

1. 0.1c
   
2. 0.5c
   
3. 0.75c
   
4. (square root of 3/4) times c
   
5. 1.0c