CAA: Christian Anime Alliance

A 65-kg petty thief wants to escape from a third-story jail window. Unfortunately, a makeshift rope made of sheets tied together can support a mass of only 57 kg. How might the thief use this "rope" to escape? Give a quantitative answer.

Okay, I'm COMPLETELY lost on this one. I have the following theories:

1. Eat less and work out until he loses 8 kg.
2. Use the rope to strangle the guards.
3. Trade the rope to a lighter thief for a stronger one that he can use.

Unfortunately, none of these have a quantitative answer. I'm THINKING this has something to do with force, since that's the chapter this problem is in, but I'm lost on how to go about this. Any help?

It's a bit of a vague question, because it doesn't tell you how much material you have to work with, or what some of the necessary dimesions are. However, if the thief had two equivalent ropes, he could anchor them to two separate points on the wall/window or whatever. Given a 65 kg weight, you will need to find the necessary angle between the ropes so that no one rope supports more than 57 kg (you should really be working in Newtons here not kg!). In other words imagine a 'V' shape, where the two ends are anchored and the thief is at the bottom of the 'V'.

Slide down the rope, but don't stop. The thief can supply 57 kg x 9.8 m/ss or about 559 N of "braking" force to counteract his weight of 65 x 9.8 = 637 N. The result is a net 78 N of force or 1.2 m/ss on his 65 kg body. I suspect that his velocity when he hits the groung will be acceptable.

Or, teleport the whole prison to the moon, where he weighs less, but the rope has the same breaking strength. Or, double up the rope (use two lengths, but that is a lot of sheets).