Jump to content
  • Advertisement
Sign in to follow this  
kelcharge

Think your smart, I thought I was...

This topic is 4845 days old which is more than the 365 day threshold we allow for new replies. Please post a new topic.

If you intended to correct an error in the post then please contact us.

Recommended Posts

Here is a math problem that I failed to solve correctly, let's see if you can. There is a metal cylinder 10 inches in diameter. The cylinder is suspended in the air on its side. At the bottom of the cylinder is a chain and at the bottom of the chain is a metal bar. It needs to be lifted 1 foot off the ground. How many degree's does the cylinder need to turn? I do not need this as an answer to homework as it was on a quiz and I missed the point, but now that I have the right answer I want to see how dumb/smart I am compared to other people and not a teacher with a book.

Share this post


Link to post
Share on other sites
Advertisement
I am not smart, but I like puzzles.

First rotate the cylinder through 90 degrees. This will have the chain hanging directly down from the side. In other words, the bar has been raised by the radius of the cylinder, 5 inches. We need another 7 inches to raise the bar by a foot. The circumference of the cylinder is 10*pi so 7/(10*pi) is the fraction of a revolution we need to continue turning the cylinder by. Since there are 360 degrees in a complete revolution this means we need to turn the cylinder by (7*360)/(10*pi) or 2520/(10*pi) degrees, which is about 80.2 degrees. So, in total the cylinder has to rotate 170.2 degrees.

Anyway, that's my spin on it [smile]

-Josh

Share this post


Link to post
Share on other sites
Guest Anonymous Poster
Answer reversed to not spoil it for the rest of you mathletes.

.ytxis derdnuh eerht semit net revo owt sulp yteniN

Could be wrong, too. This is just my first impulse.

Share this post


Link to post
Share on other sites
Quote:
Original post by Drew_Benton
My guess is ~137°


Better not be! I'll have to beat the OP with my logic stick! [wink]


-Josh

Share this post


Link to post
Share on other sites
My probaly wrong solution.
137.51 degrees

C=2*r*pi

10*pi=31.42'

12'/31.42'=0.382 or 12' would equal a 38.2% turn of the cylinder.

38.2% * 360 degrees = 137.51 degrees.

Share this post


Link to post
Share on other sites
Quote:
Original post by jjd
Better not be! I'll have to beat the OP with my logic stick! [wink]


Well, I should have put my "educated guess" - which now thinking about is wron I think. Here's what I did:

Arc Len = 2*pi*r*arc measure/360
So I solved for when the arc length is 12 (inches) and got that answer. However, I'm thinking that the wrapping of the chain around the cylinder would require more turns then I have accounted for. I don't know, we'll see!

At least someone else, Kestrel, got what I did [wink]. I just used pi as 3.1415 and didn't bother with accurate decimals.

Share this post


Link to post
Share on other sites
I think that it you take into account gravity pulling the chain away from the bottom of the cylinder as it turns it should be 170.2. If the chain and cylinder were magnetized then it would wrap tightly around it and you get 137.

Share this post


Link to post
Share on other sites
Sign in to follow this  

  • Advertisement
×

Important Information

By using GameDev.net, you agree to our community Guidelines, Terms of Use, and Privacy Policy.

GameDev.net is your game development community. Create an account for your GameDev Portfolio and participate in the largest developer community in the games industry.

Sign me up!