# Tag Archives: lab

## Speeding Problem?

The Problem:
New playing fields are going to be built on the lot across the street from our school. Unfortunately, people will need to cross Route 121 (a 2-lane highway) to get to those fields. ﻿ Currently, the proposed pedestrian crossing is a crosswalk with a flashing yellow light. Is there a speeding problem on Route 121? Do you think the proposed crossing is adequate?

﻿The Solution:
We are videoing the traffic in front of the school with Flip cams and analyzing the videos in LoggerPro. Luckily, the fence posts are 10 feet apart and are perfect for setting the scale in the analysis!

(Feed readers may need to click through to view embedded video.)

If the school had put a police officer or a “Your Speed Is…” sign in front of the school, people would slow down, and the data would not be representative of real traffic. We hope that by recording traffic from a distance, drivers will be more likely to maintain their true speed. We also hope to collect lots of data during different times of the day (different classes) to help in our analysis.

This simple activity serves as an introduction to video analysis, so students will have another data collection and analysis tool at their disposal for future labs of their own design.

## Fortune Fish

I’ve used these as the first lab of the year, like this teacher:

Reblogged from my post at wcydwt-science | http://wcydwt.posterous.com/

## How Long is the Roll?

Note: Some readers may need to click through to view the embedded video.

My conceptual physics class was chugging along just fine the other day. Then a kid asked for some paper towel. When I took out a giant roll from under the sink, the day’s lesson took a detour which would make Dan Meyer proud.

Kid: “Whoa! How long would it be if you unrolled the whole thing?”

Me: “I don’t know…you want to find out?”

Kid: “Yeah!”

Me: “OK. But you’ll need to make a prediction first.”

How long is the giant roll?

Takin' data with a smaller roll

Class data. Groups measured different amounts of paper towel. Who will be closest to the actual roll length?

Time to unroll!

Final analysis with an attempted shot at evidence-based reasoning.

## Eratosthenes 2.0

In case you missed it, fellow physics teacher John Burk blogged a post-mortem of our collaborative lesson in which our students brought Eratosthenes’s famous experiment into the 21st Century: Measuring the Earth with Skype and a Stick. The feedback from his students were overwhelmingly positive! Check it out! (And be sure to subscribe to his blog while you’re there!)

## SBG Free & Clear

Assessment is a dirty job. That’s why there’s SBG Free & Clear® with Morale-LiftersTM.

With SBG, teachers are FREE to assess and re-assess what they want, when they want, and how they want without worrying about many points should an assignment or problem be worth and how will it taint the quarter grade.

Here’s a quiz I gave last year on constant velocity motion. Before SBG I would agonize over assigning point values and had agita trying to give partial credit. The SBG version simply links the problems to the standards. A single problem can address multiple standards. A single standard can be assessed with multiple problems. SBG sets you free!

Two problems, one standard: Students must be able to tell me both Larry’s distance (problem 1a) and displacement (problem 1b) in order to demonstrate mastery of standard CV.1

Two standards, one problem: Students must be able to interpret the position-time graph given (standard CV.6) and be able to draw the corresponding motion map (standard CV.4) in order successfully answer problem 2a.

SBG has reassesment naturally built in. After the quiz above, we continued our work on constant velocity motion. The unit concluded with a lab practicum in which students simulated the tortoise and the hare story with 2 toy buggies, one fast and one slow. The “tortoise” had was given a head start, and students had to determine where and when the hare would pass the tortoise. If you scroll to the second page, you can see this is the first time for assessing CV.8 and the second time for CV.6.

You can also see that SBG gives students the opportunity to be assessed both on lab process standards and constant velocity content standards in the same assignment. You cannot mix and match standards this way with traditional grading. In the past, I would have lumped everything together as a “lab grade.”

Later in the year, when we are doing momentum conservation, I can reassess on some of the constant velocity standards to check for retention. If you scroll to the second page, you’ll see that CV.4, CV.6, and CV.7 are reassessed again.

With SBG, students are FREE to re-assess what they want, when they want, and how they want without worrying about how their past performance will impact their grade.

Here’s what one former student had to say about SBG:

I am very happy with the grading system for two reasons. A) it fosters success, and I believe that improves confidence. B) Physics is not easy. I, and I believe most students, do not always get it the first time. Being able to be graded on what we ultimately know improves my own stress-level, but by going over certain topics, I also get to know and understand them better.

As you can see,this level of freedom gives SBG its morale-lifting action.

With SBG, teachers are FREE to assign homework without worrying about how to grade it and what to do when students copy homework from each other. Teachers do not have to collect a stack of copied work, take several hours to mark them, only to return them the next day to end up in the blue recycling bin.

With SBG, students are FREE to tackle homework.for the sake of practice without worrying about performance. And students are free to choose not do homework if they do not need the practice.

A word of caution: You must trust your students and they must trust you in order for students to take ungraded homework seriously. Read about what happened when I broke that trust in an earlier post titled SBG and Trust.

SBG makes it CLEAR to teachers which of their assignments are meaningful. Does this assignment help students become more proficient in my standards? Can this assignment be used to assess students on my standards? If the answer is no, away it goes! SBG puts a stop to baseless extra credit and pointless crossword puzzles.

For example, in the past, I would give extra credit for students who submitted an entry for the Physics Challenge Problems that are in each issue of The Physics Teacher magazine, the High School Physics Photo Contest, or the Toy Box Physics Video Contest. The extra credit would usually be something like dropping their lowest quiz grade, exemption from an uncompleted homework assignment, or just extra points added to their quiz average.

Now with SBG, I can still have students enter those contests, but I will assess their entries based on the standards that apply. Hopefully, they will chose a topic they are weak on and use the contest as an opportunity to grow and to demonstrate to me that growth. Now students have another method to show me what they know outside of a quiz and get credit for it — more morale-lifing action!

SBG makes it CLEAR to students what they need to know and be able to do in order to be successful. With a list of standards give to students at the start of each unit, they do not have to second-guess what will be on the test.   Students also know exactly why their assignments are important.

SBG make it CLEAR to both teachers and students how students are progressing by CLEARLY pointing out strong and weak areas. This level of clarity is also part of SBG’s morale-lifting action. One of my students said:

I like the grading system because it helps you know what learning goals you need to focus on, and in what areas you need to study for the quiz. By putting them in those charts, we can also be aware of our progress at every point throughout the quarter.

You can find more student reactions to SBG in an earlier post called 31 Reasons Why Kids Like SBG.

Don’t think SBG Free & Clear® can stand up to Traditional Grading? Here’s a testimonial from Ms. Gajda about how traditional grading held her and her students back during an egg-drop competition in her class:

As they were taking apart their container to see if their egg had survived, these two students analysed the design of their container and highlighted the features of the design which made it successful. They had made a few last minute changes and they explained to me why they made those changes and how those changes improved the design. When asked, they were able to describe the physics concepts behind all the successful aspects of their design.

As they were talking, I thought to myself, “please write all this down in your lab report” because a lab report was how I was going to assess their understanding of the concepts of physics and design. But did those brilliant, eloquent explanations appear in the lab report? No. Did those students get credit for their understanding that had been demonstrated to me? Well, it wasn’t on the rubric for the lab report.

These two students weren’t unique. Another student who was able to tell me why his container had worked didn’t even submit a lab report. At that moment I knew there had to be a better way of giving credit to students for what they have mastered.

Enter SBG. Imagine now that I have a time machine and I can go back to April during my practicum. How would I deal with the same situation using SBG? For this project, I would have two forms of assessment.

• One assessment would be the lab report with which I would score the students on two standards: (1) understanding Newton’s second law and (2) demonstrated ability to effectively communicate in writing.
• Another assessment would be teacher observation or interview. I would record a score just for the student’s ability to demonstrate understanding of the relationship between force, mass and acceleration.

That’s the power of SBG Free & Clear® with Morale-LiftersTM.

(Note: My SBG Free & Clear® with Morale-LiftersTM picture at the beginning of the post is my lame attempt to parody this. Please don’t sue me!)

## Real or fake?

This video (taken from the Win/Fail Physics collection) is the beginning and the end of a mini learning cycle during my projectile motion unit. At the beginning of the unit, it’s the hook. At the end of the unit, it’s the assessment.

## Creating a need to know

By the end of their first viewing, all of my students are yelling “That’s fake! No way!”

“Where’s your evidence?” I ask. “Convince me.”

And students come up with all kinds of weak excuses like “It just LOOKS fake!” or “No one could do that!”

“No,” I say. “Convince me with physics. Justify your claim with scientific evidence.”

(*crickets chirping*)

The kids now have a need to know. They want to know if the video is real or not, but they lack the tools and knowledge to support or refute their original claim. They are now willing to go down the rabbit hole with you.

Whenever possible, I frame my lessons around the Karplus learning cycle: Exploration, Invention, and Application. (It’s nothing special. In fact, most other learning cycles like 5E, 7E, and Modeling are strikingly similar.) Instead of relying on lectures and textbooks, I use the learning cycle so students can construct the conceptual and mathematical models themselves, all within an interactive learning community.  By this point in the year, my students have been through several cycles, including constant velocity motion, accelerated motion (including vertical free-fall motion), and balanced/unbalanced forces.

## Exploration Phase

Our goal as a class is to develop a model for Kobe’s motion through the air. After some Socratic discussion, we conclude that Kobe’s motion, if real, could be similar to tossed ball. After all, both Kobe and the tossed ball only experience the downward pull of the Earth while in the air. Both Kobe and the ball move vertically and horizontally at the same time. However, as my Force Concept Inventory (FCI) results indicate, many of my students do not grasp the independence of horizontal and vertical motion. So I ask them to forget about Kobe for a minute, and we do two exploration activites:

• Pirate Treasure Hunt: Each group gets 10 directions (e.g., “Walk 44 tiles north”). What they don’t know is that all the groups have the same 10 directions arranged in different orders. However, if they follow the steps in order, they will be walking through walls and out windows. Eventually, students realize they can combine all the north-south directions and all the east-west directions and simply walk X paces west and Y paces north. The follow-up class discussion about “Why did you do that?” really gets at the independence of horizontal and vertical motion.
• Dropping/Shooting a Bullet: Student use ice cream cone shooter toys to answer the question: “When released at the same time, which hits the ground first: a horizontally shot bullet or a bullet dropped from the same height?” Predictions and justifications must be made. Some students see the connection right away. Others don’t, but the results make for great discussion afterwards.

Which hits the ground first?

## Invention Phase

Now we know that horizontal and vertical motion are independent. But we need to create (invent) a more detailed model to describe the motion of a tossed ball. But how will we get the horizontal and vertical motion data in order to create the model? Through Socratic discussion, student decide that trying to mark the position of the ball in the air as it moves won’t work. Nor will using motion detectors.  Students decide to use our Flipcams to video themselves tossing the balls and then do a video analysis of the motion in Logger Pro. (Students had done video analysis earlier in the year.) But there are still more questions:

• “Wouldn’t the motion depend on how fast the ball is tossed?”
• “Wouldn’t the motion of a tall/skinny arc be different than a low/wide arc?”
• “Wouldn’t the mass of the ball affect the motion?”

So, as a class, we decide to split up the data collection. One group will vary ball mass, another toss speed, and another arc shape. We’ll share the position vs. time and velocity vs. time graphs created and look for patterns in their shapes and in their equations. This is whole class inquiry — groups are doing different experiments and everyone’s data is needed. Everyone makes a contribution to our classroom scientific community.

Video analysis in Logger Pro (image credit: vernier.com)

After the data collection and analysis, students “whiteboard” their graphs and we have a “board meeting” where each group presents their results and then as a class we try to make connections among the groups and come to a consensus. At the end of the board meeting, the class has created a model for projectile motion:
In the horizontal direction…

• All position vs. time graphs are straight lines. The slope of the line represents the horizontal speed, which remains constant during flight.  This is like our previous model of constant velocity motion.
• All velocity vs. time graphs are flat lines. This means the horizontal acceleration is zero which matches up the horizontal position vs. time graph. Again, this is like our previous model of constant velocity motion.

In the vertical direction…

• All position vs. time graphs are in the shape of upside-down parabolas, with the time-squared coefficient being about 5 m/s/s. This is like our previous model of accelerated motion in free-fall.
• All velocity vs. time graphs have a slope of about -9.8 m/s/s. Again, this is like our previous model of accelerated motion in free-fall.

Also…

• The mass of the ball doesn’t matter. Again, this is like our previous model of accelerated motion in free-fall.
• Projectile motion is simply the combination of the constant velocity model (horizontal) and the acceleration motion model (vertical).

Presenting lab results

## Application

We are now ready to return to the Kobe Bryant video to apply the student’s newly created model for projectile motion. They decide to immediately feed the video into Logger Pro for analysis. Students are able to make a claim regarding the realness of the video, and justify that claim with evidence and reasoning. I ask them to accumulate as much evidence as possible in order to make a stronger case for their claim.

Groups that finish early are pushed further with more questions: Is Kobe’s horizontal speed reasonable? Is the vertical and horizonatal distances he leaps reasonable? How will you figure those out and make a claim to their possibility?

At the end, groups whiteboard their work again, groups present their results to the class, and we reach a class concensus. The debate here sometimes gets very heated.

And when they are all done, they still ask me, “Is it real?”

“You just figured it out yourselves!” I say. (*sigh*)

## Notes

1. Robert Karplus workshop materials on reasoning and the learning cycle.:

2. If you don’t have Flipcams, a regular digital camera that shoots movies will do fine. And if you don’t have a digital camera, there are plenty of pre-fab projectile videos to use — have a look at Dolores Gende’s collection of physics videos for analysis.

3. Levels of Inquiry. This cycle has elements of both guided (Level 2) and open (Level 3) inquiry. I stay away from confirmation/verification (Level 0) at all costs. The coupled-inquiry cycle is an easy way to do more open inquiry in class.

4. For additional information about modeling, see the Modeling Workshop Project web site at Arizona State University. Here’s a great introductory article: Modeling Instruction: An Effective Model for Science Education

5. Rhett Allain’s wonderful analysis of the Kobe Bryant video was the inspiration for this learning cycle. Thanks, Rhett!