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Re: [Phys-l] Pinewood Derby Car Weight....



At 20:56 -0800 2/24/07, Marc \"Zeke\" Kossover wrote:

Because the car rests at an angle and finishes flat, the back of the car undergoes a slightly greater change in height than the front.

OK. Apparently things have changed since my kids were doing that stuff, lo! these many years ago. My recollection is that when we did this, the time was from the start to the bottom of the track, so the cars all ended up at the same slant that they started with. Hence placement of the extra weight made no difference.

Even so, the height difference can make only a difference at the margin (although in a close race the margin counts for a lot). The big difference will be due to the larger mass reducing the effect of the air resistance. Doubling the mass reduces this effect by half and that can make a big difference, especially if the shape isn't quite aerodynamically optimum.

On the other hand, my recollection was that you weren't allowed to add any weight to the vehicle beyond what you put on by adding the wheels and a dab of paint. Maybe they have changed that rule too.

Hugh
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Hugh Haskell
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