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United States24813 Posts
As any seasoned tl blog reader would agree, physics is a topic seen most predominantly in 'help me with my hw' type threads. Physics is indeed a course that many people who lack the background or interest take due to a requirement for school/work. In fact, this effect has become so exaggerated that most people don't seem to realize just how interesting, relevant, and fundamental physics really can be (and is).
I'm not bringing this up due to some kind of attempt to be a responsible educator of physics. My motivation is more simple. I like physics, and I don't like to see it misrepresented until it drives many people to dislike it.
I have access to a nice collection of thought provoking physics questions of various levels. My plan is to post one question (multiple choice) minus the answer, and ask for people to provide in spoilers their prediction of what the answer is, and an explanation. I suppose I should pick the first response that adequately answered the question, and feature them as the previous week's winner.
I'm going to choose a question of varying difficulty from the following topics (probably will sequentially run through the topics):
Mechanics:
Kinematics
Newton's Laws of Motion
Momentum and Energy
Rotation
Gravity
Fluids
Heat
Vibrations
Light
Electricity and Magnetism
Relativity
Quanta
The goal is for every reader to encounter at least one question that is difficult enough to challenge them while being within their knowledge/ability to answer correctly. These problems are mostly simple at face value, but at times can fool even graduate students in physics programs, so don't sell them short! Upon the conclusion of the question, I will provide my own estimate of the difficulty of the question on a scale of 1-5 with 1 being easiest.
Question 1
Kinematics
Micronesia exercises his dog yubee on a 15-minute walk by throwing a stick that yubee chases and retrieves. To keep yubee running for the longest time as Micronesia walks, which way should he throw the stick?
a) In front of him
b) In back of him
c) Sideways
d) In any direction, as all are equivalent
+ Show Spoiler +Starting with an easy one that doesn't require much knowledge, but don't expect this to continue 8o
  
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+ Show Spoiler +b
throwing the stick backwards makes the dog have to cover the distance between you and the stick twice plus whataver distance you may have traveled by walking.
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+ Show Spoiler +
EDIT:
+ Show Spoiler +because you are walking forward away from the stick while yubee is fetching it so there is a longer distance for him to run to get back to you
but if its yubee you might want to throw it on a roof or something
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For question one + Show Spoiler + my first instinct is behind him because then the dog has to run in two directions, behind, then back to the owner giving the most exercise. This assumes the owner walks in the same direction the whole time.
That makes the most sense to me.
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United States24813 Posts
Feel free to post just the answer if you want, but an explanation of why you chose the answer would be nice, could illicit discussion (in spoilers I suppose), and also qualifies you for being the winnAr.
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So... you're using TL.net as a tool to measure the difficulty of problems that you intend to assign to your students? eh?
+ Show Spoiler +Ahh! I fell for the trick! It's d because it's about time. You take 15 minutes to walk. The total distance the dog runs is v*t. If you keep the dog running the entire time then nothing happens. I blame the guy who didn't spoilertag his answer
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United States24813 Posts
On September 26 2008 09:35 Hippopotamus wrote:
So... you're using TL.net as a tool to measure the difficulty of problems that you intend to assign to your students? eh?
Lol. I minimize how many problems I give to my students that require thought. Not because I don't want them to think, but because their ability to do it is generally limited (and I blame NCLB XD).
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On September 26 2008 09:35 Hippopotamus wrote: So... you're using TL.net as a tool to measure the difficulty of problems that you intend to assign to your students? eh? + Show Spoiler +Ahh! I fell for the trick! It's d because it's about time. You take 15 minutes to walk. The total distance the dog runs is v*t. If you keep the dog running the entire time then nothing happens. I blame the guy who didn't spoilertag his answer
+ Show Spoiler + yes but the dogs velocity would have to increase to catch up to you if you throw it backwards, so it's not like it's constant or anything.
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Haha I can actually think of a lot of complications with that first question. Like, can we assume that you can throw the stick equally far in any direction? Because I think I can throw it a lot farther in front of me then I can behind me. And, where's the dog when you throw it? is he right under your feet, or somewhere in front of you? And do you keep walking when you throw it?
Heh sometimes I feel like the only thing my education in physics has taught me is how to nitpick stuff like this.
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Also:
On September 26 2008 09:24 micronesia wrote:
probably will sequentially run through the topics):
Fluids
Heat
Vibrations
Who says physics isn't sexy 
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Based on the fact this is supposed to be simple, I believe a certain razor would easily explain the answer to all your questions
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Calgary26004 Posts
Nice! I spend most of my days working on fluid mechanics so I'm excited for that section! Good blog!
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On September 26 2008 09:47 Luddite wrote:Also: Show nested quote +On September 26 2008 09:24 micronesia wrote:
probably will sequentially run through the topics):
Fluids
Heat
Vibrations
Who says physics isn't sexy
I ROFL'd to that.
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+ Show Spoiler +d? assuming all else is equal, and micronesia will be tossing the stick as soon as he gets it back, then yubee will essentially be running the duration of the 15 minute walk. wait.....
i would say b, if yubee would wait (or walk with micronesia) a split second every time he brings the stick back for micronesia to wind up and throw it again. limiting this interruption would force doggy, er yubee, to spend more time running during micro's 15 minute walk.
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wow, i never knew the principle of relativity could trick so many people, assuming he's walking at constant speed of course.
+ Show Spoiler +
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+ Show Spoiler +Behind. The distance from Yubee's starting position to the place where the stick landed will always be the same and hence the time will be the same, so Micronesia wants to know how to be farthest from the stick when this time occurs, which occurs when he walks directly away from the stick.
Unless Micronesia continually throws the stick; then it doesn't really matter, although if he always takes a fixed time to throw the stick then behind still wins.
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+ Show Spoiler +Behind him, assuming that they're walking a straight path and the dog slows down when he picks up the stick and returns it. The dog will have a longer return trip than any of the other directions.
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O RLY?
Remember this timeless truth:
It's only physics if the deer are perfectly spherical and there is no air resistance!
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United States24813 Posts
On September 26 2008 11:29 Hippopotamus wrote: O RLY? Remember this timeless truth: Show nested quote +It's only physics if the deer are perfectly spherical and there is no air resistance!
The perfectly spherical one I'll give you, but I've had to do too much air resistance for you to say that!
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On September 26 2008 19:33 micronesia wrote:Show nested quote +On September 26 2008 11:29 Hippopotamus wrote: O RLY? Remember this timeless truth: It's only physics if the deer are perfectly spherical and there is no air resistance! The perfectly spherical one I'll give you, but I've had to do too much air resistance for you to say that!
haha, but back in grade school/etc, they always ignored air resistance and it made me so fucking mad.
They'd be like "John is riding on the back of a pickup truck. He throws a ball straight up in teh air while moving forward at 40 mph. When the ball comes back down, where will it land?"
And obviously the REAL answer is behind him because of air resistance, but those asshole teachers were always like "NO IT LANDS BACK IN HIS HANDS LOLOL U LOSE"
so I'm like fuck how about we go try it out to prove it and they're like "YOU GET AN F"
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EPT
