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Dirt
A guy who was cleaning his house realized his vacuum uses more power than a box fan, so he got creative and grabbed a lawn mower bag and the hose from the vacuum and taped those to the front and back of his box fan respectively. However, when he went to use his new contraption, the dust never went into the bag. Why is that?
Answer
Box fans don't suck. Since they lack the sucking power of vacuums, it can't suck the dirt into the mower bag. Any dirt that happens to make it in would end up on the fan parts and wouldn't make it into the bag.Hide Answer Show Answer
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Comments
Hmm, I'm not buying it. The suction of a vacuum is only because air is being moved and the only available source for it is the small tube. If you moved the same amount of air and guaranteed that the only source for more air was the tube, you'd get suction there, too.
The problem with a box fan is that the back of the fan is not the only source of air. If you restrict it, then the air will come from the front of the fan, moving around the edge of the blades. They don't meet the cylinder that they are in as closely as the fan portion of a vacuum.
The other problem with the whole setup is that the lawnmower bag is not permeable, or not very, anyway. Therefore, the air would be even more resistant to flow through the whole thing.
The problem with a box fan is that the back of the fan is not the only source of air. If you restrict it, then the air will come from the front of the fan, moving around the edge of the blades. They don't meet the cylinder that they are in as closely as the fan portion of a vacuum.
The other problem with the whole setup is that the lawnmower bag is not permeable, or not very, anyway. Therefore, the air would be even more resistant to flow through the whole thing.
Not nearly enough detail on this. Even Zag gave the benefit of the doubt and assumed that using a bunch of duct tape or something the back of the fan is restricted to only pull air through the tube. That's not in the teaser. Which is fine, but then I would have wanted a better description of what makes a vacuum work in the answer to distringuish it from the contraption.
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