I am compiling a list of interview questions to use in the future. I decided to search some websites to see if there were any questions I would like to use in my interview tomorrow. Check out the link and then tell me how you would answer #11.
Please read the link before proceeding to the rest of the post.
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Nathan's comment made me think too...so what did I do? I googled the question, "Why is there fuzz on a tennis ball?" and go the following answer.
The fuzz, more properly called felt, is usually made of wool treated with various additives to make it last longer and resist staining.
http://tennis.about.com/od/tennisballfaq/f/faqballs019.htm
The tennis ball cover is rough but not like sandpaper. Looking closely at the felt you can see that air flows through those raised fabric filaments - better known as fuzz. So the surface of a tennis ball is a "porous surface." It's more like dealing with the wind blowing through leaves on a tree and just as complicated. The fuzz filaments act like tiny cylinders each having their own drag component. In addition to the skin friction drag from the cover itself, drag is created from the airflow over these fuzz fibers interacting with all the other fibers behind it. Rabi Mehta dubbed this phenomenon "fuzz drag."Experiments Mehta conducted also showed that as the ball speed increases the fuzz filaments lay down on the ball and the fuzz drag declines. Here are two pictures from the wind tunnel test. You can see in the picture on the right that the fuzz is closer to the ball's surface. The air passing over the ball on the left is about 45 mph, while on the ball on the right the air is 135 mph.
http://www.tennisserver.com/set/set_01_10.html
Researcher Rabi Mehta, working with students, discovered that the "fuzz" on a tennis ball created more drag than was previously believed, since each individual fuzz filament contributes to drag. In addition, he found that fuzz drag is particularly interesting since the fuzz filaments can change orientation during play and gradually wear off.
http://www.nasaexplores.com/show2_articlea.php
I am still wondering why you would ask this question in an interview? To test someones ability to formulate an answer on the spot? What other odd questions have YOU been asked during an interview?
5 comments:
Huh, I don't really know. I suppose maybe the fuzz helps it grip, or helps with ball rotation, or maybe spin. But I'm really not sure. Do you know why? Now you've piqued my interest.
I'm sure it has something to do with the grip/rotation but I am not sure why you ask that unless you were interviewing someone to work at a tennis ball factory.
It's all about how someone thinks - one question that was apparently asked at Microsoft is "How many piano tuners are there in Chicago". - Tyler
So now, thanks to Google, we know all about the physics of the fuzz on a tennis ball, but WHY is it there? We still never really arrived at an answer...
I might not be able to sleep tonight for not knowing the answer to this one!
J/Kzzzzzzzzzzz
It does have something to do with grip and rotation. The felt creates drag and reduces bounce which allows the players to manipulate the path of the ball more easily. If it were smooth like a superball, no one could control it reliably. And it's basically used in interviews to assess the way someone thinks. Even if you didn't know the answer, it's perfectly okay to answer, "That's an interesting question. I suppose maybe the fuzz helps it grip..." Same as asking why humans have an appendix, or why basketballs have bumps and golf balls have dimples. Analytical thinking. :)
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