Worst TAing/Teaching experience.

[maverick_starstrider]

Hi,

I don't mean to bash hard working undergrads but I would be curious to hear other peoples worst/dumbest/funniest teaching or marking experience.

I'll start things off with a quick one:

-I was once marking the hwk assignment of a first year physics class and one particular student had written something akin to:

$ds=cos(x)\rightarrow \frac{ds}{s}=co(x) \rightarrow d=co(x)$ or in non-LaTeX: ds=cos(x) -> ds/s = co(x) -> d=co(x).

In other words they actually factored the s out of cos (and out of ds). I have to say, I had to stare at that paper for a couple minutes in disbelief.

Anyone else got some good ones?

 

[Pengwuino]

[itex] ds=cos(x)\rightarrow \frac{ds}{s}=co(x) \rightarrow d=co(x)

That's GOLD!

A friend of mine always had this great example of funny things undergrads did. He wrote a quiz and it was mainly give-away points. One question was something like "If a line makes a 90 degree angle with another line, the lines are considered:" and the solutions were A) Perpentangular B) Perpendicular C) Tangentdicular and D) Tangentangular . Of course, people actually picked solutions other then B.

 

[cristo]

-I was once marking the hwk assignment of a first year physics class and one particular student had written something akin to:

At least it was a first year physics class. I've seen similar from second and third years!

 

[junglebeast]

Hi,

$ds=cos(x)\rightarrow \frac{ds}{s}=co(x) \rightarrow d=co(x)$ or in non-LaTeX: ds=cos(x) -> ds/s = co(x) -> d=co(x).

Anyone else got some good ones?

That looks like a case for FailBlog to me if I ever saw one!

 

[Chi Meson]

That looks like a case for FailBlog to me if I ever saw one!

Most readers of Failblog would not know what was wrong with it.

I kinda weep for that student. He/she probably did really really well in high school physics only to find that the class they took was a watered down physical science class that spent three months on kinematics ("we don't go on until everyone understands what 'acceleration' is").

Probably got an 'A' without ever using a trig function, and so "cos" must have been "displacement x heat capacity x some other variable."

I just had a students who, on three different occasions, in three different assignments (one was even a test) gave a "short response" answer that completely contradicted itself. One was like this (paraphrasing here):

[Question: "Explain why a neutral pith ball will be attracted to a negatively charged rod."]
Answer: "A Neutral pith ball can never be attracted to a negatively charged rod because it is neutral. Only a positively charged pith ball will be attracted to a negatively charged rod. This will cause induction, and the neutral pith ball will be attracted to the negatively charged rod."

 

[NeoDevin]

This was from several 3rd year students:

$i\hbar\geq\frac{\hbar}{2}$

 

[Topher925]

I once had a group of students turn in a lab report where they had written out all of their equations and sample calculations on a white board hanging on someones refrigerator. They took pictures of the white board with the equations written on it and then pasted them into their lab report. They didn't even bother to crop out the pizza coupons out of the picture which were hanging right next to the white board on the refrigerator.

 

[fleem]

Once a student of mine couldn't remember the word "oscilloscope", so they referred to it as a "laboratory television".

 

[Topher925]

Once a student of mine couldn't remember the word "oscilloscope", so they referred to it as a "laboratory television".

HAHA! I'm stealing that one.

 

[maverick_starstrider]

This isn't really my anecdote but does everyone here know the heavy boots anecdote? I tell it to my students sometimes when they make a similar mistake. It basically goes like this:

A professor asks a first year student "Is there gravity on the moon?". The student then thinks on this a bit an replies confidently "No". The professor then asks the student "Really? We've all seen footage of men walking on the moon. How is this possible if not through gravity?". The student, again, sit and ponders a moment before then, again confidently, states "Heavy boots?"

 

[maverick_starstrider]

Oh, I also once had a first year student who I'd never talked to before ask me if I'd give an expert testimony to beat a criminal speed racing charge. They were like "could you tell them that you're a physicist and that, like, them radar guns are really unreliable"... Awkward.

 

[G01]

I have a couple gems from my days as an undergrad tutor:

"Do I really need to memorize both of these formulas for the frequency of an LC circuit:

Formula 1: $$\omega=\frac{1}{\sqrt{LC}}$$

Formula 2: $$\omega=\sqrt{\frac{1}{LC}}$$

I also had a student do the following calculations in an induction problem:

$$\frac{dI}{dt}=$$cancel the d's=$$\frac{I}{t}$$

The sad part was he had passed Calc 1 and 2.

During an optics problem, I had a student who had trouble finding the correct focal length for a lens:

object distance = 2
image distance = 2

so therefore:

$$\frac{1}{o}+\frac{1}{i}=\frac{1}{f}$$

$$\frac{1}{2}+\frac{1}{2}=\frac{1}{4}$$

Obviously, the focal length was not 4. The student could not figure out why.

 

[Pengwuino]

Once a student of mine couldn't remember the word "oscilloscope", so they referred to it as a "laboratory television".

I'm going to try to use that term as often as possible in my master's project thesis thingy.

 

[junglebeast]

$$\frac{1}{2}+\frac{1}{2}=\frac{1}{4}$$

Obviously, the focal length was not 4. The student could not figure out why.

It doesn't actually mean the student didn't know how to add fractions. I think we all make silly math mistakes sometimes...just like sometimes I put the cereal in the fridge and the milk in the cupboard

I think it's when something becomes so incredibly easy and basic that the mind stops allocating any actual "thought" to the process and just let's basic instinct take over, which is more of a pattern-matching thing and sometimes matches the wrong pattern...so even when you stare directly at it, you're like...what? It looks right? Because you only see what you are expecting to see.

 

[Redbelly98]

This isn't really my anecdote but does everyone here know the heavy boots anecdote? I tell it to my students sometimes when they make a similar mistake. It basically goes like this:

A professor asks a first year student "Is there gravity on the moon?". The student then thinks on this a bit an replies confidently "No". The professor then asks the student "Really? We've all seen footage of men walking on the moon. How is this possible if not through gravity?". The student, again, sit and ponders a moment before then, again confidently, states "Heavy boots?"

Here's the version of that story that I'm familiar with:
http://www.phys.ufl.edu/~det/phy2060/heavyboots.html
This version is actually contrary to the theme of this thread, as two undergrads are dumbfounded when a philosophy grad TA claims that Heavy Boots are what prevented the Apollo astronauts from floating off into space during their moon walks.

 

[Pengwuino]

Here's the version of that story that I'm familiar with:
http://www.phys.ufl.edu/~det/phy2060/heavyboots.html
This version is actually contrary to the theme of this thread, as two undergrads are dumbfounded when a philosophy grad TA claims that Heavy Boots are what prevented the Apollo astronauts from floating off into space during their moon walks.

This is NOT rare! We've had this story from people in our own university about people in the graduate programs around the campus thinking like that. My immediate response to the heavy boots would have been "What about the Moon's gravity?"... although I have a feeling I would have gotten a response that had to do with the atmosphere...

 

[bassplayer142]

that ds one was classic lol.

http://www.jimmyr.com/blog/Funny_Student_Math_Mistakes_258_2006.php

 

[Moonbear]

It doesn't actually mean the student didn't know how to add fractions. I think we all make silly math mistakes sometimes...just like sometimes I put the cereal in the fridge and the milk in the cupboard

I agree. I cannot tell you how many times I got an exam question wrong because I would write something like 3x3=6. It's the sort of mistake that it's hard to even catch when proofreading, because your eyes just gloss over it. Those kinds of mistakes just make me cringe and feel sorry for the student.

When I was a TA, we used to have a list of the funniest exam answers we'd pass around and add a few to it each year. I don't remember too many of them anymore.

I haven't seen any really good, funny ones in a while.

 

[arunma]

Here's a funny one. Dang, I wish I'd made a scanned image of this.

When I was TAing the first semester of calculus based physics, there was a homework problem with some electric charge distributed over an arc of a circle subtending a given angle, and the students had to calculate the electric field at the center. A lot of students couldn't do it. But one decided to entertain me instead of just turning in a blank homework. He drew this picture of a "Homework Solving Machine." It was a big monitor with wings on the sides and a funnel on the top. You put the homework in the funnel, press the "solve" button, and then out comes your solution!

I couldn't give him any points, but I had to give him props for that one.

 

[Astronuc]

There are some quantities that must always be positive. One cannot have a negative number of apples, for example. Similarly when solving for a neutron flux in a reactor, one should not get a negative number of neutrons. But I had three grad students calculate a negative flux in a homework problem. They had picked the wrong trigonometric function when solving a second order differential equation because of a misapplication of boundary conditions.

 

[Pengwuino]

There are some quantities that must always be positive. One cannot have a negative number of apples, for example. Similarly when solving for a neutron flux in a reactor, one should not get a negative number of neutrons. But I had three grad students calculate a negative flux in a homework problem. They had picked the wrong trigonometric function when solving a second order differential equation because of a misapplication of boundary conditions.

Kinda like masses falling upwards in gravitational fields

I know one fellow grad student who tends to supply me with great examples of common sense going out the window. You know energies with units of meters or position expectation values that have a 1/x term in it who's limit did indeed blow up.

 

[Astronuc]

Kinda like masses falling upwards in gravitational fields

or getting negative mass and not realizing that there is something wrong with that.

 

[Pengwuino]

or getting negative mass and not realizing that there is something wrong with that.

Oh yah! or negative volumes! I'm surprised how common negative masses are.

 

[rootX]

or getting negative mass and not realizing that there is something wrong with that.

This looks possible (electrons/holes).Once someone asked me what is recursive function and other time a group of three people didn't know how to integrate a linear line (we had done two calculus courses by that time) but the problem was from other course so they couldn't make connection.

 

[Office_Shredder]

that ds one was classic lol.

http://www.jimmyr.com/blog/Funny_Student_Math_Mistakes_258_2006.php

$$\lim_{x \rightarrow 8} \frac{1}{x-8} \neq \infty$$

 

[Redbelly98]

When I was a lab TA, a number of labs involved plotting data and then estimating the slope of the line. This one student kept getting the wrong slope. The third time this happened, I realized he was just using the grid boxes on the graph paper for his units to calculate "rise over run". The actual units, that he indicated clearly in the axis labels, did not enter into the slope calculation.

 

[junglebeast]

When I was a lab TA, a number of labs involved plotting data and then estimating the slope of the line. This one student kept getting the wrong slope. The third time this happened, I realized he was just using the grid boxes on the graph paper for his units to calculate "rise over run". The actual units, that he indicated clearly in the axis labels, did not enter into the slope calculation.

That's not overly stupid considering that his method would work if the graph wasnt stretched or squished

 

[Chi Meson]

Kinda like masses falling upwards in gravitational fields

I know one fellow grad student who tends to supply me with great examples of common sense going out the window. You know energies with units of meters or position expectation values that have a 1/x term in it who's limit did indeed blow up.

I had an AP Physics student who, in answering a buoyancy question, designed an experiment featuring rock floating in water, being held below the surface by a string tied to the bottom of the bucket.

 

[Redbelly98]

That's not overly stupid considering that his method would work if the graph wasnt stretched or squished

It would only work if each grid box was 1 unit, i.e. 1 m, 1 kg, 1 N, etc. Which they almost never are.

 

[junglebeast]

It would only work if each grid box was 1 unit, i.e. 1 m, 1 kg, 1 N, etc. Which they almost never are.

You are incorrect. It will work with any units, as long the as the graph is not stretched or squished, because slope is a ratio.

 

[Redbelly98]

You are incorrect. It will work with any units, as long the as the graph is not stretched or squished, because slope is a ratio.

I think you misunderstood what I was saying.

For example, we could have been graphing displacement vs. time, and want to calculate the slope in order to find the velocity.

Suppose the plotted line goes 2 grid boxes upward for every 1 grid box to the right, and each vertical grid represents 0.1 m and horizontal grid boxes represent 0.5 seconds each. The slope of that line would be

(2 × 0.1 m) / (1 × 0.5 s)
= 0.2 / 0.5 m/s
= 0.4 m/s​

However, my student would just use the grid boxes and said the slope is 2/1 or 2.

 

[junglebeast]

Suppose the plotted line goes 2 grid boxes upward for every 1 grid box to the right, and each vertical grid represents 0.1 m and horizontal grid boxes represent 0.5 seconds each. The slope of that line would be

(2 × 0.1 m) / (1 × 0.5 s)
= 0.2 / 0.5 m/s
= 0.4 m/s

However, my student would just use the grid boxes and said the slope is 2/1 or 2.

Yes, that is a stretched graph...but if each grid cell was X units wide and X units tall (for any X), then you could just count the number of boxes for rise over run to get the slope. This will work for any choice of units as well.

 

[Redbelly98]

Since one axis is measuring displacement and the other axis measures time (in my earlier example), it is impossible for them to be the same unit.

 

[junglebeast]

Since one axis is measuring displacement and the other axis measures time (in my earlier example), it is impossible for them to be the same unit.

I was not talking about your graph specifically, just pointing out that the method of determining slope by counting grid squares will work for graphs with any combination of units; so for example, not only will it work if the unit in both axis is "0.1 meters" but it will also work if the vertical axis has units of "0.1 meters" and the horizontal axis has units of "0.1 seconds". In both of these cases it will give correct slope in terms of "meters per second." Additionally, it will work to give a correct slope even on "stretched" graphs, although the units are then different. This was the mistake made by your student: he calculated a numerically meaningful value for slope, but it was no longer in the units you were expecting.

 

[MATLABdude]

I thought I'd take it nice and easy one semester, focus on research, and not TA. Then they asked me to mark for a computer interfacing course I'd never taken. "It won't be too bad, there's a marking guide, only 5 or 6 assignments [about 1 per fortnight] and it's right up your alley! -ish. Plus you're the only one remotely capable who isn't assigned to something else."

Turns out the prof was teaching 2 other courses, and dealing with various personal issues at the time (sickness / death of a relative, etc.) So no assignment solutions. And the course wasn't quite as easy (based on what I'd done previously) as I had hoped. Long story short, I ended up showing up to class, making model solutions, obsessing over model solutions to try to make sure I was right (to be fair, the prof would glance over my model solutions to make sure I was on the right track), and then marking 40ish assignments. That sucked.

So a few days before the final, I get some e-mails asking if I can get the prof to post the model solutions? I ask if he can post his model solutions (he'd said that he'd take care of it) and then he responds by asking if I can give him my model solutions! Not totally unreasonable, but I was caught off-guard by this. So after hauling butt and getting the solutions corrected and typed up that day, I give them to him for posting (approximately a week before the final).

Finito, it leaves my mind. So all of a sudden, I get a few more panicked e-mails asking when the solutions will be posted, so I e-mail him suggesting that maybe he should send an e-mail out to the students pointing out that the solutions were posted on my website. During the weekend before the final (Saturday night, or Sunday afternoon, I forget which, final on Monday), they show up on his website.

Moral of the story: know what you're jumping into! And nice and easy is never correlated with jumping into the unknown. I think I ended up putting in 3 or 4 times my allotted 3 hours per week (they paid us by the hour, but you only got so many hours) as a result of that course.