Comical mistakes in your homework.

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Tautology
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Comical mistakes in your homework.

Postby Tautology » Mon Mar 09, 2009 2:14 pm UTC

I much prefer making mistakes in Physics homework than in Maths homework, because when I screw up a calculation, half the time it leads to situations that are pretty funny to imagine. This is most apparent in anything to do with Astrophysics.

I once managed to calculate that the radius of the Sun was so big that it engulfed the entire solar system. Another time, I proved that a comet was travelling at almost twice the speed of light as it intersected the Earth's orbit. I once embarrassingly implied that a very small meteorite that barely managed to get through the atmosphere hitting the Earth would create a crater with a diameter of roughly 2 Earth radii. Oh dear.

However, I believe that this graph made in Computational Physics (supposedly graphing a forced harmonic oscillator's motion) is one of the sexiest mistakes I've ever made:

Spoiler:
DSC00002.jpg
It was so beautiful that I felt kind of sad when I fixed the problem.
DSC00002.jpg (54.05 KiB) Viewed 11098 times


So, has anyone else ever fundamentally screwed over the laws of physics and lived to tell the tale?

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ian
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Re: Comical mistakes in your homework.

Postby ian » Mon Mar 09, 2009 5:31 pm UTC

I...what? What mistake did you make that came up with that?

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Tautology
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Re: Comical mistakes in your homework.

Postby Tautology » Mon Mar 09, 2009 6:17 pm UTC

Well, the graph is plotting the angle on the y-axis in radians. I wanted to keep the angle between 0 and 2[imath]\pi[/imath], so if the angle was greater than 2[imath]\pi[/imath] it would subtract 2[imath]\pi[/imath] from that value and so on. Unfortunately, I accidentally said that if the angle was greater than [imath]\pi[/imath] to subtract 2[imath]\pi[/imath], and if it was less than [imath]\pi[/imath] to add 2[imath]\pi[/imath]. This meant that unless the angle was exactly [imath]\pi[/imath], it was going to be changed. Hence, an amazingly screwed up graph.

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Re: Comical mistakes in your homework.

Postby The Boz » Mon Mar 09, 2009 6:54 pm UTC

Physics exam, last year. An angled shot problem. Where does a 1kg projectile fired with an initial speed of such and such at an angle of so and so land on an irregular surface pictured on an image. The image represented a landscape with a rectangular drop, a steep hill, a cliff and a mountain, and it's far end was marked with one thousand meters. So the projectile shouldn't fly for more than a thousand meters, right? Well, I have no idea how exactly I did it, but somehow I came to the conclusion that the projectile has reached escape velocity. With no time to find my error, I wrote on the exam: "I think I missed a minus somewhere, because my projectile is currently orbiting the Earth." On the oral exam, the professor had a good chuckle out of it :)
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Uber_Apple
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Re: Comical mistakes in your homework.

Postby Uber_Apple » Mon Mar 09, 2009 7:06 pm UTC

not actually my work but i saw it displayed on a wall in chemistry:
'Oxygen is our main source of air'

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Re: Comical mistakes in your homework.

Postby Link » Tue Mar 10, 2009 9:13 am UTC

This wasn't a mistake on my part, but rather one in my textbook. I don't remember the exact figures, but it was something like this: "12 identical Christmas lights are connected in parallel. Each bulb has an approximately ohmic resistance of 24Ω. The lights attach to the wall socket, which provides 230V. Find the power drawn by each bulb." Apparently these people are trying to decorate their Xmas trees with searchlights :lol: .

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Re: Comical mistakes in your homework.

Postby SmashtheVan » Tue Mar 10, 2009 12:08 pm UTC

Link wrote:This wasn't a mistake on my part, but rather one in my textbook. I don't remember the exact figures, but it was something like this: "12 identical Christmas lights are connected in parallel. Each bulb has an approximately ohmic resistance of 24Ω. The lights attach to the wall socket, which provides 230V. Find the power drawn by each bulb." Apparently these people are trying to decorate their Xmas trees with searchlights :¡This cheese is burning me!: .


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Re: Comical mistakes in your homework.

Postby nilkemorya » Tue Mar 10, 2009 3:23 pm UTC

I think the best one I ever saw was when some low level physics students I was helping(no calc physics) came up with a fish that was traveling at 36000 miles per hour, and they didn't see the problem with it. That's one fast fish!
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Re: Comical mistakes in your homework.

Postby Link » Tue Mar 10, 2009 4:45 pm UTC

nilkemorya wrote:I think the best one I ever saw was when some low level physics students I was helping(no calc physics) came up with a fish that was traveling at 36000 miles per hour, and they didn't see the problem with it. That's one fast fish!
"Und I prezent zu you, ze ultimate zupervillain: Relativistic Fish!"

Reminds me of this:
Spoiler:
Image

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Re: Comical mistakes in your homework.

Postby achan1058 » Tue Mar 10, 2009 5:01 pm UTC

nilkemorya wrote:I think the best one I ever saw was when some low level physics students I was helping(no calc physics) came up with a fish that was traveling at 36000 miles per hour, and they didn't see the problem with it. That's one fast fish!
I have seen a few similar ones when I was grading. Something about a camera rotating at 1 million rev/second.

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Re: Comical mistakes in your homework.

Postby Robert'); DROP TABLE *; » Tue Mar 10, 2009 5:17 pm UTC

I can't remember how, but the phrase "frequency of the material" appeared in my physics homework.
...And that is how we know the Earth to be banana-shaped.

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Re: Comical mistakes in your homework.

Postby Talith » Tue Mar 10, 2009 6:18 pm UTC

There's something satisfying about knowing that the earth is 3E9 m.s^2.kg^-1 old..... If you ask me unit mistakes are always the best ones :).

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Re: Comical mistakes in your homework.

Postby Dobblesworth » Tue Mar 10, 2009 8:50 pm UTC

In a random electronics question dealing with the 'complex' reactive power when you have inductance and capacitance loading, the situation involved, among other things, one parallel branch of the overall system consisting of "four 100W light-bulbs" [in the question statement]. Circuit diagram I provided to analyse the problem had me draw that individual branch wired in series. It didn't affect my answer, but the supervisor marking it commented "in practise these would be wired in parallel". During the supervision, I replied, "they could be Christmas lights", and we were sidetracked for 20 minutes as we discussed the ramifications of a Christmas tree light system built as such.

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Re: Comical mistakes in your homework.

Postby rho » Tue Mar 10, 2009 10:39 pm UTC

"Organism."
"Orgasm."

It's an easy mistake for an 11 year old to make.
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Re: Comical mistakes in your homework.

Postby ST47 » Tue Mar 10, 2009 10:50 pm UTC

I had someone ask me if impulse and momentum had the same units today. And then argue that they didn't.

I also somehow managed to work out in a calorimetry lab that my cheeto was storing more chemical energy than your average country consumed in its lifetime.

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Re: Comical mistakes in your homework.

Postby watch_wait_plot » Tue Mar 10, 2009 10:54 pm UTC

"Organism."
"Orgasm."

It's an easy mistake for an 11 year old to make.


*wince*
Yeah, it was great when my biology teacher (a sixty-ish year old woman) made that little screw up.

I had a problem earlier this year where I had to calculate the maximum speed achieved by a a jumper on a trampoline, given the spring constants, his weight, and the initial height. My answer was greater than the escape velocity of the solar system. :D

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Re: Comical mistakes in your homework.

Postby Mighty Jalapeno » Tue Mar 10, 2009 10:55 pm UTC

I'm not sure exactly which portion of the calculation I input wrong, but the end result was that a glulam beam 24" deep to span a given space was something like 18 feet wide, which basically meant I was putting down a two-lane bridge made of wood. I was running out of time on the test, so I just put that down as my answer (since 70% of the marks is the work involved, and there was just ONE error there) and added a little side note: "Boy, I bet you wish you'd gone with a steel building!"

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Re: Comical mistakes in your homework.

Postby Zeroignite » Wed Mar 11, 2009 12:31 am UTC

From a buddy in 8th grade:
"So, we have the initial amount of radioactive stuff, and he wants us to find the percentage remaining after a few years? Wait, I know how to do this....
*does math*
"So, after 15 years the isotope is <hits enter on calculator> 12.7829 million percent!?! of the original?
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Re: Comical mistakes in your homework.

Postby Other_Calvin » Wed Mar 11, 2009 2:51 am UTC

I hope this is the right thread, though it probably is, because there isn't a "how my textbook screwed up" thread.

The AP chemistry textbook our school uses says that 1 amu = 1.660538782 kg, in addition to giving Pascals as [imath]kg/m^{2}s[/imath].

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Re: Comical mistakes in your homework.

Postby Zeroignite » Wed Mar 11, 2009 2:59 am UTC

Other_Calvin wrote:1 amu = 1.660538782 kg, in addition to giving Pascals as kg.m2s.
What. The. Fuck!
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Re: Comical mistakes in your homework.

Postby Domus Ulixes » Wed Mar 11, 2009 8:23 am UTC

I once had a mathematician student claiming atom's could easily emit light with an energy far below h-bar/100...

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Re: Comical mistakes in your homework.

Postby iznih » Sat Mar 14, 2009 1:50 am UTC

my favourite mistake:
theoretical physics, i was trying to solve a differential equation, somewhere that appeared:
[math]\frac{\gamma}{\omega_0^2 - \omega^2 }[/math]
and i wrote: [math]=0 \longrightarrow \omega_0^2 = \omega^2[/math]

it got a special place on a wall in the faculty building :D

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Re: Comical mistakes in your homework.

Postby uknowurright9 » Sat Mar 14, 2009 4:56 am UTC

I was balancing an equation in AP chem last year and somehow ended up with an element on the product side that wasn't present in the reactants in any form whatsoever. Not only did I end up with this element apparently being "created" but I also managed to "destroy" an element that was present in the reactants. I spent about 15 minutes starring blankly at it trying to figure out how it happened before I realized I had cancelled coefficients of two different elements with one another resulting in an epic fail. :P

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Re: Comical mistakes in your homework.

Postby Hit3k » Sat Mar 14, 2009 5:51 am UTC

I was once doing some calculations to find the gravitational force between two bodies I ended up eliminating all variables in the equation and ended up with something like:
1253 = 3.
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Re: Comical mistakes in your homework.

Postby Carnildo » Sat Mar 14, 2009 7:12 am UTC

Not on my homework, but on the homework of someone I was helping in high-school chem class:
Cl2 -> C + I2

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Re: Comical mistakes in your homework.

Postby defaultusername » Sat Mar 14, 2009 4:15 pm UTC

My high school chemistry text-book tries to explain resonance by demonstrating it in benzene:
Resonance.GIF
Because phlogiston.

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Re: Comical mistakes in your homework.

Postby BirkettBoy » Sat Mar 14, 2009 9:20 pm UTC

So far? my Biology teacher saying that Diffusion requires:

"Absolutely NO ENERGY"

(Ok so not shouting "no energy" but you get the gist)

and to be fair, out of a group of GCSE students, I was the only one who had any idea why spherical farm animals and cats in Physics are funny, so I guess they wouldn't know why this is so obsered...but seriously?? No Energy???!

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Re: Comical mistakes in your homework.

Postby semicharmed » Sun Mar 15, 2009 12:13 am UTC

BirkettBoy wrote:So far? my Biology teacher saying that Diffusion requires:

"Absolutely NO ENERGY"

(Ok so not shouting "no energy" but you get the gist)


Actually, in biology terms, he's right, as diffusion relies solely on the difference in concentration gradients on opposite sides on the membranes. So in terms of the cell, no ATP has to be expended for transport to happen

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Re: Comical mistakes in your homework.

Postby sigsfried » Sun Mar 15, 2009 12:53 am UTC

Routinely replace the word element with the word elephant. Resulting in the best sentence ever:

"The infintessimally charged elephant undergoing thermal expansion ..." in the explanation of how I had set up the problem .

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Re: Comical mistakes in your homework.

Postby Ratio » Sun Mar 15, 2009 11:15 am UTC

Due to making a negative power a positive one by mistake, I once ended up with a protien molecule bigger than the know universe.

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Re: Comical mistakes in your homework.

Postby Alexius » Sun Mar 15, 2009 2:40 pm UTC

sigsfried wrote:Routinely replace the word element with the word elephant. Resulting in the best sentence ever:

"The infintessimally charged elephant undergoing thermal expansion ..." in the explanation of how I had set up the problem .

One of my chemistry teachers did that once- "So if you look at the properties of the carbonates and nitrates of all the elephants..."

A biology lecturer claimed to have narrowly missed putting up a silide titled "IMMORALITY IS A RARE PRIVILEGE"

And aged about 11, I accidentally wrote about the Battle of Hastings at which the Normans defeated the Saxophones.

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Re: Comical mistakes in your homework.

Postby Turtle_ » Sun Mar 15, 2009 3:03 pm UTC

In my Government class we had to find how much government spending on one thing increased over some amount of years. It increased from some amount to something around 20 times as big. A lot of people were convinced that it was a 5% increase...
"Sometimes lies were more dependable than the truth." ~ Ender's Game
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Re: Comical mistakes in your homework.

Postby wst » Sun Mar 15, 2009 6:08 pm UTC

Once during an assessed practical I ended up with the value of g being 0.56ms^-2. I said to the teacher afterwards that I couldn't even have missed out a power of 10 and got it right.

And that was way beyond experimental error as well...
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Re: Comical mistakes in your homework.

Postby Uber_Apple » Sun Mar 15, 2009 6:47 pm UTC

not really homework and quite a long time ago probably when i was in year 1 or something:

I found a piece of paper with a drawing of me and my father puhsing me on a swing and underneath the caption read in huge crayon letters: 'Me and my Bad go to the park'
[grammar nazis will find 2 jokes here].

Physics: after a long, long calculation i managed to calculate that an electron was travelling at 1.4 x 1012ms-1 and was really happy that i had finally finished the question until i looked at the power.

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Re: Comical mistakes in your homework.

Postby Charlie! » Sun Mar 15, 2009 10:01 pm UTC

So on a physics problem I recently answered that to tunnel through a barrier only a few volts high and a nanometer long (with expected value 1) you'd need to throw so many electrons at it that the electrons would weigh more than the mass of the earth.

Fun times.
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Re: Comical mistakes in your homework.

Postby achan1058 » Mon Mar 16, 2009 7:40 pm UTC

I recalled a physics problem given by a computer problem generation system that asked me to calculate the position of the bear on a plank given the mass of the plank and the bear, and the length of the plank, and some other conditions on the force. When I was done with the problem, I found that the bear was levitating a few meters to 1 side of the plank, and still exerting force on it. The teacher was amused, but told me to enter the answer anyways, since the system is too stupid to tell that there is a problem.

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Re: Comical mistakes in your homework.

Postby She » Mon Mar 16, 2009 10:49 pm UTC

I have once been asked to calculate the gravitational constant given some numbers on speed on water running out of a tap. It should have been 9.8, but instead became 9800. I dind't have time to correct it, so I simply wrote "There is an error somewhere in here."
And anyways, I like my constant better, cause it's over 9000.
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Re: Comical mistakes in your homework.

Postby Jianaran » Mon Mar 16, 2009 11:00 pm UTC

Doing some trigonometry a long time ago that involved monkeys with inclinometers sitting in trees, I worked out that the tree was 2.5km tall.

It turned out my answer was right, and our teacher had intended it to be that way.

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Re: Comical mistakes in your homework.

Postby Carnildo » Tue Mar 17, 2009 6:02 am UTC

She wrote:I have once been asked to calculate the gravitational constant given some numbers on speed on water running out of a tap. It should have been 9.8, but instead became 9800. I dind't have time to correct it, so I simply wrote "There is an error somewhere in here."


I would guess you mistook millimeters for meters.

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Re: Comical mistakes in your homework.

Postby Gojoe » Tue Mar 17, 2009 6:17 am UTC

Before a French exam, my friends and I memorized how to say the equivalent of the elephant farm is beautiful in may. And we put that as the answer of any question we did not know.
michaelandjimi wrote:Oh Mr Gojoe
I won't make fun of your mojo.
Though in this fora I serenade you
I really only do it to aid you.
*Various positive comments on your masculinity
That continue on into infinity*

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