I have a character who needs to get down a pit of unknown depth in a limited amount of time (about 1 hour).
To check the how far it goes down, I have him drop a electric lamp in the pit, reasoning that it will shatter at the bottom. It's nearly completely dark, there's no air, but an Earth-like gravity. I figure it would take the lamp about 41 seconds to fall 5 miles and 57 seconds to fall 10 miles. Correct?
The character has a very long, thick carbon-fiber cable, but no proper climbing gear. With what speed would he be able to climb down? Does 5 miles per hour sound reasonable? Or is that unrealistically slow?
He also has some scraps from which he can construct a simple abseil mechanism (Uh... how do you call the mechanism that lets an elevator travel down a cable?). I've found the world record in speed rappelling is 100 m in 9 seconds. Could he keep up that kind of speed over a longer distance? (Note: cable and mechanism are designed for a high-speed elevator, so I don't think they'd overheat) Is there a chance for him to get down 10 miles in about half an hour or less this way?
And if he just jumps, it should take him the same amount of time as the lamp to reach the bottom, right?