2010-09-02

Easy Month: A Ton of Feathers

It's time for another of the fabled Theme Months, and this month, despite lack of better judgement, Bengt has decided to do something truly wild and uncharacteristic and give you some problems that are in fact not insanely difficult! Let us savour the moment. The idea is that these problems should be possible to solve not only without a degree in science, but also without a calculator.

There's an old joke which goes: "Which is heavier, a ton of lead or a ton of feathers? Drop it on your toes and you'll see!" Now, for some reason, Bengt has got himself a big cube of some sort of fabric material stuffed with feathers. He's has some vague plans of using it in a giant board game, but for now, he amuses himself by dropping it on his feet. There's no need to worry; it doesn't hurt at all. But having a scientific and somewhat peculiar mind, he wants to find out just how fast the cube is falling when it hits his foot. The cube is 1 m high, and we can ignore air friction and the height of Bengt's toes.

  1. Suppose Bengt drops the cube from 1m. What is the speed when it hits his toes?
  2. Suppose instead that he balances the cube on its edge, and lets it fall. At which speed will the fastest part of the cube move when it hits his toes?
  3. Suppose he instead balances it on a corner?
  4. If you put them on a pair of (very large) scales, which would seem to be heavier, a ton of lead or a ton of feathers?