The Weasel King ([info]theweaselking) wrote,
@ 2007-01-25 08:38:00
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But the question is so *easy*, even without the elephant.

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[info]scifantasy
2007-01-25 02:04 pm UTC (link)
What gets me is, he was there. He had both critical equations.

And part 2 is a joke. Frictionless!

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[info]silmaril
2007-01-25 02:06 pm UTC (link)
But I'd have given it at least a point for creativity, nonetheless. (If not for the equations, which as you pointed out he already did have.)

Maybe it was one of those "no partial credit" exams.

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[info]theweaselking
2007-01-25 02:14 pm UTC (link)
One of my TAs, way back when, told me of a class in which the final question on the exam was to have a weight compressing air in a bottle - determine how much the air heats up.

He arrived at this question with 2 minutes to go in the time alloted.

Step 1: Assume air is incompressible.
Step 2: The temperature will not change.

He got 2/15 on the question, for having a correct answer given his assumptions.

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[info]scifantasy
2007-01-25 02:36 pm UTC (link)
Maybe it was one of those "no partial credit" exams.

I can't stand those. I'd have given the guy...well, I'm generous. But maybe four points for having the right equations for step 1, and a point for the elephant.

Unless the zero was because the elephant insulted the grader's sensibilities.

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[info]affreca
2007-01-25 02:53 pm UTC (link)
Physics exams need to be partial credit, because so much is in the process, not just the final answer. I would have given points for the elephant, because it makes me smile.

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[info]sebkha
2007-01-25 03:40 pm UTC (link)
I had to mark something like this once. A student submitted a Rube Goldberg design for an electronics design assignment that involved an attitude adjustment ferret. He drew a pretty good cartoon ferret as part of the schematic.

I was honor-bound to give him a mark for that.

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[info]chaosrah
2007-01-25 02:28 pm UTC (link)
haha, next time i don't know the answer in physics, I'm going to try that. I totally failed my physics test yesterday... Urg.

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[info]gothpanda
2007-01-25 03:52 pm UTC (link)
Once I got half-credit on an Honors Physics exam question by writing down every single equation I could think of. I had no frakkin' clue which one to use, but the professor figured hey, I was trying, right?

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[info]jaffa_tamarin
2007-01-25 03:02 pm UTC (link)
Insufficient data. Need to know length of spring as an upper bound for x.

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[info]jaffa_tamarin
2007-01-25 03:06 pm UTC (link)
Also, answer to part b is obviously no. An object that has come to rest is clearly not continuing to move. It may, however, start moving again.

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[info]theweaselking
2007-01-25 03:16 pm UTC (link)
But *after* it comes to rest is the question. At the moment it comes to rest, it is not moving. *After* it comes to rest, even an infinitesimal time later, will it or will it not be moving?

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[info]theweaselking
2007-01-25 03:12 pm UTC (link)
No, you don't. You just need to assume there is no upper bound for x, as the question does.

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[info]jaffa_tamarin
2007-01-25 04:37 pm UTC (link)
The diagram clearly shows the spring to be of finite length. If the question wishes me to assume the length is sufficient not to affect the calculation of x, the question should say so. I am training to be a physicist, not a mind-reader.

There appears to be some distance between the foot of the ramp and the spring. Do I need to calculate for air resistance effects, or am I also to assume this all takes place in a vacuum?

Won't the vacuum kill the elephant?

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[info]theweaselking
2007-01-25 05:38 pm UTC (link)
Diagram: It also very clearly shows that x is significantly less than the length of the spring.

Air resistance: If the plane is frictionless, then so is the air.

And dead elephants stop falling blocks just as well as live ones. Better, even, in some cases.

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[info]theweaselking
2007-01-25 06:54 pm UTC (link)
PS: The worst thing is, it's a frictionless surface.

This means that the block will stop and the elephant will start moving.[1]

And then the elephant will compress the spring - to the exact distance that the block would have, because it's frictionless.


[1]: assuming, of course, that elephants are not, themselves, springy. Since no k is given for the elephant, the assumption of a solid uniform non-springy elephant is actually a pretty workable one.

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[info]siouxsyn
2007-01-28 01:19 am UTC (link)
And would give exactly the same answer as the original problem. The question refers to the object, and if said object changes in transit....

I was daydreaming about a gravity free situation too, where the elephant would just sail back up the ramp. Yes.

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[info]ryusen
2007-01-25 06:10 pm UTC (link)
My HS Physics teacher enjoyed placing Cats into his word problems... especially the ones that involved Kinetic Energy.

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[info]tsunami_ryuu
2007-01-25 08:27 pm UTC (link)
Hah! That reminds me of a student last year who knew he was going to withdraw from Organic Chemistry but due to the timing of his withdrawl had to take the class's first exam. He did stuff like this to all the questions -- stick figure Chuck Norris art included -- and in one problem space rewrote from memory the entirety of Carroll's "The Jabberwocky". He's something of a school legend now.

I think he scored a few points by the end... actually, upon checking, I see it was four points.

Here are some sample pages of his great work, as published in the school newspaper.

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[info]toku666
2007-01-26 10:21 pm UTC (link)
The most memorable physics problem I ever had on a test was back in high school:

It involved a situation where a lion has started to pounce onto a hunter. Given the force of his jump, and his mass, as well as the mass of the hunter's bullets, we had to calculate (assuming infinite oppurtunity to fire on the hunter's part) how many shots would need to be fired to stop the lion before it collided with the hunter.

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