It’s summer, so there may be a soapbox derby in your community on an upcoming weekend. Here's something I've always wanted to know: should a soapbox car be heavy or light.
You might instinctively say, "light," because all things being equal, lighter cars are faster.
...but that's when you have an engine pushing the car's mass. In this case, it's gravity pulling the car down. So the weight shouldn't matter, because, as Galileo showed, things fall at the same speed, regardless of mass.
...but that's in a vacuum. In an atmosphere, heavier things fall faster, because they have more force to overcome aerodynamic drag. So a heavier car would be faster.
...but, a heavier car will have more rolling resistance, because the weight of the car will be pushing down on the axles, increasing the friction.
I tried googling this question once before and never got a straight answer. I tried again just now and found someone with experience had answered this. Yes, there are engineers with extensive experience with soapbox cars; surely that’s not a surprise. The answer is, it depends.
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