I teach elementary science, so the impulse momentum theorem isn’t something have to I deal with- but I’m intrigued with the idea of video-based assessment, so here goes:

Option 1:
This question is a yes/no closed response, so it seems like it would only require a simple application of a formula. I did countless problems like this in undergrad engineering, and know from personal experience that it’s quite easy to apply formulas to questions like this and get correct answers without any understanding of the underlying concept. So this question is assessing computational ability only- not everything we’re looking for as a science teacher.

Option 2 and 3:
Insufficient information is given in both of these to simply plug and play with the equation (I believe) and the questions are asking to explain rather than solve. This *should* provide evidence of actual understanding- however I know that this evidence is often limited by the thoroughness of the student’s response. For example, what if the student doesn’t actually apply the formula of the impulse-momentum theorem in their answer, but only discusses the general idea. Ideally, as a teacher I would like to see that students understand both the concept and application of the formula- so including both types of questions on an assessment would be helpful.

Comparing Options 2 and 3- it’s interesting that the video version introduces the problem details a little more subtly, because the student will be focused on the image of the jumper as well. It doesn’t explicitly explain how the airbag compresses over a period of time, which would be a big hint for students that we’re talking about an integral. Option 2 still reads like a word problem, even though it’s asking for an explanation. So I think students would be more likely to give a mathematical response to Option 2, whereas with Option 3 you may only get an explanation of the general concept.

I’m not sure it’s possible to effectively assess both the computational skill and the conceptual understanding aspect in the same question- so I would personally use two questions (like Option 1 and Option 3) to address both of these areas.

So one video is used to assess the last question. While in some circles this may be uniques, I don’t really see it as anything out of the ordinary.

Having students create video responses as answers…now that would be phenomenal.

I have 15 science education blogs on my blogroll (right-hand sidebar of my blog). They mostly have similar pedagogic styles to the math education blogs I read, but they have more focus on inquiry and they use video more directly as data for everyday labs, rather than as inspiring stories the way Dan does.

I think #1 is a “can you get there from here?” assessment. Good for determining whether someone can grind numbers but not great at assessing whether someone really understands how the numbers relate.

Two’s a little hand-holdey for me. That’s something I’d expect more in a discussion/introduction to the concept than in assessment. If you need that much coddling to get to the core point here – which I’d say is that it’s all about the delta – then the student getting the answer right doesn’t tell me much.

I like three but I wouldn’t give it to a student who didn’t reasonably have an expectation of what sort of answer would pass muster. As written “because it slows him down” would seem to barely quality. “Because it slows him down more slowly than hitting the hard ground” is better.

I think I’d ask for some observations about something you see in the video that support your answer, hoping to hear something about how thick the bag is and I’d be excited to hear something about all the visible vents on the bag that allow it to deflate at a particular speed.

Melanie: I’ll be the first to admit that using video for assessment in this way isn’t unique–even Jeopardy has “video” daily doubles. But video’s strength as an assessment tool is not a function of uniqueness. Rather, its strength lies in its potential to quickly and thoroughly probe for conceptual understanding. What I find most attractive about using video for assessment is the simplicity of it–this is something that any teacher can do, even those with a limited technical background or under heavy pressure to hit all the standards in time. Organizing and executing a project in which students create their own video-answers is for the select few teachers who have technical expertise and the flexibility to integrate it into their curriculum. But using video for assessment is for the masses.

Nick: No data to share yet, unfortunately. I’ll be formally collecting data on this sort of thing during the upcoming school year though, and I’ll keep you posted (if you remind me!) I’m right there with you with what you said about needed two questions to assess both conceptual and mathematical understanding. My tests and quizzes have a mix of both. I’d like to see examples of some quality questions that manage to assess both, I’m sure they’re out there.

Joe: You didn’t “[make] reference to the impulse-momentum theorem,” so you would get a zero and a little frowny face next to your answer. Kidding aside, I should mention that the students have seen good, thorough answers to video-based conceptual questions modeled for them before such questions show up on quizzes and tests.

I teach middle school level physics and chemistry and I think this is a fantastic approach to problems that students might otherwise find difficult due to the presence of formulae, words, numbers, etc. (yes, I’m serious). The video assessment presents the situation in the same way the student would confront it in the real world and would help them to achieve understanding beyond a basic mathematically-based knowledge of the situation. I find that students understand a lot more about physics than they think they do, mostly based on what they’ve experienced outside of class. It’s often the numbers, equations, and vocabulary that mucks things up for them.

Option 1 calls for all that meaty-looking math that generally passes for understanding. It’s traditional — in both a good and bad way. Kids who practice at solving traditional problems can pass traditional tests. Achievement within the system is something my students rarely experience and I don’t take lightly. But wow, a kid good at repeating algorithms sure can convince you he knows some physics.

Option 2 over-explains. Sure, there’s a real application in there but it’s buried in all those numbers. I was bored reading the problem.

Option 2 loses the meaty math, which I think is a shame. I’ve struggled with problems like this because kids often stop at the conceptual answer. How can we lower a framework of “make some reasonable assumptions and give me some kind of numeric answer” onto this problem? Man, that would be the best of all possible worlds.

@Megan: I think you can have it both ways (Options 1 and 3) if you simply add “Provide both a conceptual explanation and a back-of-the-envelope calculation. Be sure to describe any approximations and simplifying assumptions you made in your analysis.” What do you think?

The textbook I use in AP Physics C (“Matter and Interactions”) frequently asks students to do these types of analyses. Here’s an example straight from the text:

“Two students who are late for tests are running to classes in opposite directions as fast as they can. They turn a corner, run into each other head-on, and crumple into a heap on the ground. Using physics principles, estimate the force that one student exerts on the other during the collision. You will need to estimate some quantities; give reasons for your choices and provide checks showing that your estimates are physically reasonable.”

In my experience, kids freeze up when they see these types of questions initially. It takes practice for them to feel comfortable making up reasonable values and assumptions.

I like option 3 the best, but as some have pointed out, it may be necessary to add the world ‘quantitatively’ to the prompt.

@Frank: Thanks for the tip to encourage “back of the envelope calculations” to show conceptual & mathematical understanding.

@luke: Yes, in many of your “answers” I see students who kind of understand the material parroting back something I said in class. I call this the spaghetti method — throw a bunch of ideas on the test and see what sticks. This is where I favor Frank’s idea to include back-of-the-envelope calculations to apply the math to their understanding of the video.

On the aspect of video-as-assessment, I say “bravo”. But then, the deck was stacked in favor of video, wasn’t it? For the sake of assessment, I need to put this video in each kids’ hands to play and replay as needed. When they need to. Hmm, I wonder what tech I could do this with most economically.

Luke: Here’s how I’d grade your answers, out of 4 points.

1) The force is applied for a long time because of the air bag. The i-m theorem is F dt = m dv, so the stunt person will survive.

1/4. You don’t mention that the long time of impact results in *less* force. Stating the formula without further explanation is insignificant. In general, if you apply a force of a longer period of time you have a greater change on momentum.

2) The stunt person takes some time to stop after they land on the air bag.

0/4. The stunt person would also take some time to stop if they hit the pavement. You need to talk about the differences between these times and what the implications for force are.

3) The force on the stuntman will be relatively small because the stunt person slows down gradually due to the airbag.

2/4. You’re correct, but you’re not making reference to the I-M theorem. Add another sentence to the effect of “The stuntman will experience a large change in momentum as he comes to a stop, a change which according to the I-M theorem is equal to (average) force times time, so the larger t is the smaller F will be.”

4) The i-m theorem is F = m dv/dt, and the airbag increases dt, and therefore decreases F.

4/4. Though this answer is brief, it’s clear you’ve been able to precisely describe the mathematical/conceptual basics of the physics going on in the video.

5) The i-m theorem is F = m dv/dt, and the airbag increases dt, and therefore decreases F. If the stunt person landed on the sidewalk, they would stop almost instantly — dt would be very small.

4/4. Only thing that I would consider adding is “dt would be very small, making F very large.” to the end, but is a 4/4 answer already in my book.

6) The airbag reduces the acceleration experienced by the stunt person.

0/4. This is true, but you need to explain *how* it reduces the acceleration–and explanation that would involve the I-M theorem–and also how lower acceleration translates into reduced potential for injury.

7) A given change in momentum (stunt person coming to a stop) can be accomplished by a large force over a short amount of time (side walk landing) or a smaller force over a longer amount of time (air bag landing).

4/4. It’s fine that you don’t state the I-M theorem as a formula, because you’ve stated it with words. Your additions in parentheses connect the formula to the video, demonstrating understanding.

Ross: Here’s an example of a video you might be able to use regarding place value/units: Verizon Math Fail (http://www.youtube.com/watch?v=ANDk0SWzplo)

You could use this video to introduce the topic, by showing it at the beginning of the unit and facilitating a discussion about just where the miscommunication between customer and customer service rep is coming from.

For assessment, you could use this video at the end of the unit, asking students to explain who is in the right–customer or customer service rep–and why, and/or determine how much the customer would think he owes and how much the representative would think he owes if some other given quantity of data was downloaded.

Gee, I wish I had gotten here earlier.

Assessing them, I’d say each has its role and you have foolishly listed them in order of increasing complexity.

Option 1:

This is a primitive problem, one that I would put in on-line homework to be sure they have done the reading. What makes it the most basic of problems is that it gives you all of the numbers needed to apply Fdt = mdv, and nothing else. No distractors of any kind.

Option 2:

I think this tests the concept, but not conceptual understanding. What I like about this version is that it has an excellent distractor in that the only number given is irrelevant to the impulse-momentum theorem. It dangles bait that suggests work-energy (or even work-impulse) in front of the student. Although you mention time, the student has to CHOOSE between time and distance when analyzing the problem. Force is not mentioned at all, so its importance has to be recognized by the student.

True, it is too wordy, but that can be fixed. Could even have a drawing.

Option 3:

The only difference between Option 2 and Option 3 is that the student has to identify all of the key variables from knowing the theorem, not from the quantities given in the problem itself. (BTW, that could make this version easier because students should start from the theorem rather than the data, so they won’t waste time trying to find some way of using the distance given in Option 2.)

I won’t go so far as to say that it does a better job of testing conceptual understanding, because it tells them which principle to apply. A better question would simply ask why the stuntwoman survives, letting them choose the one that is most relevant. After all, an expert would look at the question and say “this is usually used as an impulse-momentum problem with a known speed, but conservation of energy is the best way to determine the ratio of the height of the crane to the height of the air bag if I know I can land on my back.”

Comment:

No mention of your rubric. Is choosing the height of the crane part of your ideal answer?

Off topic digression:

Firing an automatic weapon is a much cleaner example, and these days I usually have several students (both male and female) in any given class who have extensive experience with fully automatic weapons and can share with the class their experience of average force resulting from a series of impulses.

I know this thread is dead, but since it inspired me to try video assessment out myself, here’s what I came up with: http://scientificteacher.com/2011/08/31/video-assessment-killed-the-clip-art-star/