Saturday, September 4, 2010

Classic Logic Problem

Assuming that it always raining at the same clip, and that your starting point is a garage covering your car, and your ending point is another garage that will cover your car at your destination, and that there is only open space being showered upon by the rain between the two points...

To minimize the number of rain drops striking the car between the two points, is it better to drive the car fast or slow?


  1. I'll answer, assuming that 'classic' means that its a real logic problem and you are not going to take the liberty of pulling a little factoid out of your hat that makes me look like I am answering the question prematurely, without enough thought.

    Using simple tricks to simplify the situation (rather than steady general shower, have the rain fall at rate of 1 drop every 5 feet, and your car is 10 feet, ignoring car contour . . . assuming car is nothing but a 3d box, collecting water, shooting from the hip, I say faster is better. Taking things to extreme, one care driving 1 mile/hour for 500 mile rainy trip, or 500 mile/hour for 500 mile rainy trip, yes you are rushing ahead to go catch the next drop that you wouldn't have run into, goind slower, but you are also not 'back there' collecting the raindrop that the slow care is catching yada yada yada. Lets say the shower is in the form of 5000 streams of water, such as you would see coming out of the tap where enough water is coming out to keep the stream solid, rather than broken up. Number of streams is finite. one every 10th of mile, water is coming down at the same rate in every stream, per your 'raining at the same clip' rule. . . . without putting it to the calculator, i say it minimizes rain drops striking the care going fast.

  2. Just for your entertainment, it occurred to me that if the car were as thin as paper, perpendicular to the direction of travel, then SLOW SPEED minimizes the number of rain drop hits.

  3. We shall now delve into the concept of 2 dimensional people capable of driving such a car, and maintaining a requirement that the driver be alive. uh, that was a requirement, wasn't it?