Physics, Boats, and Interview Questions

By now we’re all familiar with the crazy interview questions given potential Google and Microsoft employees (and anybody who’s ever interviewed with me.) Often times they’re not even closely related to the job, but they’re good at seeing somebody’s thought process.

By now every programmer should know how to solve the lightbulb problem or the bridge problem by memory, and we’re pretty good at estimating the height of the empire state building in quarters (and how many sodas that would buy.) A few of us have even estimated the number of gas stations in the US and then looked it up to see we were close - it’s over 200,000.

But there’s one that I just can’t prove either way… and I don’t remember enough college physics to prove it.

Here’s the question:
You’re on a boat in the ocean and you throw a very heavy suitcase overboard. Does the boat rise in the water?

I can make a compelling argument for either side, but I want to know what side is correct.

Can anybody prove this using math and physics? I’d be interested to see how.

I’m leaving up north today for a wedding, and then I’m in Seattle next week.. but I’ll check in to see if anybody has an answer for me.

September 21st, 2007