Spring and Rope Puzzle Answer

mechanical diagram When you cut the supporting rope, the weight moves up one meter! Now it is only ten meters below the support. Here is what the system looks like when everything comes to rest (click image for larger view).

Now that the springs are separated, each is holding up only half of the weight, so only one Newton of force stretches each spring. Since the length of each spring is one meter plus two meters for each Newton of force, each spring is now three meters long. Together with a seven-meter rope, this makes ten meters. That's one meter higher than the weight was before.

Look at the puzzle again.

Copyright 1996 by Eric Postpischil.