Mars and math
Feb. 12th, 2004 04:39 pm![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png){kind=small}
essentialsaltesLatest Mars photo from the rover.
Math puzzle for the day.
You have a sphere. A cylindrical hole is drilled through the center of the sphere. The length of the hole from end to end is 6 cm. What is the volume of the pierced sphere?
It's wacky... you don't need to know the radius of the sphere or the radius of the hole. Confused? This answer is not likely to help much.
Math puzzle for the day.
You have a sphere. A cylindrical hole is drilled through the center of the sphere. The length of the hole from end to end is 6 cm. What is the volume of the pierced sphere?
It's wacky... you don't need to know the radius of the sphere or the radius of the hole. Confused? This answer is not likely to help much.
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no subject
Date: 2004-02-12 08:08 pm (UTC)Re:
Date: 2004-02-13 03:11 pm (UTC)I think that describes a good fraction of your physics homeworks.
The lazy physicist way to do the problem is to say, "well, if it doesn't matter what the radius of the sphere is, then I'll pick a sphere with diameter 6cm. Then the hole will be a hair thin little line through it, which won't take any volume away. So the 'leftover' volume is the same as a sphere of radius 3 = 36pi cc.
That guy does some wicked solid geometry that I don't remember, but I got the answer by doing some calculus: the 'washer' method of calculating volumes of solids of revolution.
Fortunately, I won't bore you with more detail, because you're still working on derivatives, and the washer method uses integrals.
Re:
Date: 2004-02-13 08:06 pm (UTC)