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# Physics / Calculus III Problem

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### #1J. Faraday  Members   -  Reputation: 118

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Posted 13 October 2013 - 01:57 PM

You are in outer space in a spaceship at location (2, -3, 1) that has run out of fuel, drifting in space in the direction of <-1, 1, 2> at a speed of sqrt(6)mph. You need to be re-equipped with power and supplies. The closest supply station is located at (10, 5, 10) and it sends out a supply vessel perpendicular to your projected line of flight.

a) What is the minimal distance to your line of flight?

b) What direction did the supply package take?

c) In terms of your flight parameter, t = time (in hours), when does this closest approach occur?

d) Where is this interception point?

I need help with this problem.

I figured that some of you may want some practice on this, and seeing as how I can visualize this problem but I do not know the proper steps to take, it could be helpful to all of us.

### #2Tom Sloper  Moderators   -  Reputation: 6514

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Posted 13 October 2013 - 05:55 PM

Mr. or Ms. Faraday, are you a student? And is this a problem you have to solve for class?

-- Tom Sloper
Sloperama Productions
Making games fun and getting them done.
www.sloperama.com

Please do not PM me. My email address is easy to find, but note that I do not give private advice.

### #3PeterStock  Members   -  Reputation: 339

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Posted 14 October 2013 - 07:28 AM

I figured that some of you may want some practice on this, and seeing as how I can visualize this problem but I do not know the proper steps to take, it could be helpful to all of us.

You should ditch physics and go into politics.

### #4Álvaro  Crossbones+   -  Reputation: 8104

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Posted 14 October 2013 - 07:59 AM

You shouldn't use English units when doing computations in space: http://www.cnn.com/TECH/space/9909/30/mars.metric.02/

### #5Paradigm Shifter  Crossbones+   -  Reputation: 4064

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Posted 14 October 2013 - 01:22 PM

Those units are obsolete, thanks to modern media. We have 3 standards for length now in the UK (newspaper/popular science reports):

Length of a double decker bus

Furlongs

Distance to the Moon

occasionally we add the height of Big Ben (which is of course incorrect, Big Ben is the Bell and the tower which holds the bell isn't called Big Ben). (Distance from elbow to fingertip was popular but is deemed "too French" by most of the media except the Guardian which insists on those units throughout).

For area of course we use either the area of a football pitch (small) or area the size of Wales (big, usually the standard unit of rainforest deforestation).

Volume there are no set standards but size of an elephant (African variety) and dimensions of a double decker bus (filled with custard) are also commonly found, and often used for mass calculations.

This is a homework question though, so the prof probably expects the answer in furlongs per fortnight.

Edited by Paradigm Shifter, 14 October 2013 - 01:27 PM.

"Most people think, great God will come from the sky, take away everything, and make everybody feel high" - Bob Marley

### #6J. Faraday  Members   -  Reputation: 118

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Posted 14 October 2013 - 07:08 PM

I am a student and I am solving this for my OpenGL class, it's a homework problem. I need to solve it using Calculus first, then later in the semester I'll have to use OpenGL to solve this problem. I have tried to take the Projection of A (<8,8,9>) onto B (<-1, 1, 2>) which would be the vector of the shadow of A onto B in the B direction (which we will call vector C). Then I subtracted C from Vector A which is supposed to give me the vector perpendicular to the vector A (the closest possible point of intersection). So from this, I should have (a) solved, which is the magnitude of ||A-C||, and (b) which is -(A-C), the direction of travel of the package. I do not know if this is the correct method however.

Finally, I cannot figure out how to calculate the time in which this occurs. ©

I should have been more descriptive from the beginning, so I apologize.

### #7Paradigm Shifter  Crossbones+   -  Reputation: 4064

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Posted 14 October 2013 - 09:15 PM

OK, give me some time to solve your homework problem on my free time for free and stuffs, I'll get right back to you.

"Most people think, great God will come from the sky, take away everything, and make everybody feel high" - Bob Marley

### #8J. Faraday  Members   -  Reputation: 118

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Posted 14 October 2013 - 09:47 PM

All I was doing was asking for help. No one asked you specifically to help. Just because you have absolutely no idea how to solve this, which no matter what reply you make to this could convince me otherwise, doesn't mean you should cover up your lack of interest in solving a problem like this (or knowledge thereof for that matter) by stating such a silly remark.

I, for one, gain pleasure from solving problems like this, because I know it is expanding my knowledge and mental capacity, so I wanted to share it with everyone. I also just wanted to point out that this entire forum is to "help people in your free time for free and stuffs.", which is how the entire forum process works.

I just wanted to point out your insolence in an objective way. I figured out the problem on my own, anyway.  Funny how you'd waste your time posting a long reply to something you don't have time for.

Regards,

### #9Paradigm Shifter  Crossbones+   -  Reputation: 4064

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Posted 14 October 2013 - 10:05 PM

Good then. Well done you *golf clap*. I solved your problem and got an A+, and stuffs, but since you worked it out yourself the satisfaction of that is worth even more. And stuffs.

"Most people think, great God will come from the sky, take away everything, and make everybody feel high" - Bob Marley

### #10unbird  Crossbones+   -  Reputation: 3483

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Posted 15 October 2013 - 12:31 AM

Off topic: Since nobody mentioned it: It violates forum rules to ask for homework solutions. That's why you got such reactions. I think there's a certain tolerance though if you show that you actually tried it yourself, got stuck then and ask for a specific detail, sort of like in your second post.

Edited by unbird, 15 October 2013 - 12:32 AM.

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