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Day 67: Marshmallow Puff Tube

 

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College-Prep Physics: We did an exploratory activity as an introduction to impulse. Another single-sentence lab:

LAB 13 — Marshmallow Puff Tube
Design several mini-experiments to determine the factors that affect the speed of the marshmallow.

Here’s the results from one group.

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Sadly, no one thought to change the mass of the marshmallow:

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More info about building marshmallow puff tubes:
http://www.exploratorium.edu/snacks/marshmallow_puff/

NGSS Science and Engineering Practices:
#3. Planning and carrying out investigations

Day 60: Another Single-Sentence Lab

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AP Physics C: Yesterday I wrote about a single-sentence lab we did in College-Prep Physics. We also did a single-sentence lab in AP yesterday and today:

Determine the rotational inertia of a bowling ball using 2 different and independent methods.

NGSS Science and Engineering Practices:
#3. Planning and carrying out investigations
#4. Analyzing and interpreting data
#5. Using mathematics and computational thinking
#7. Engaging in argument from evidence

Day 59: A Single-Sentence Lab

College-Prep Physics: Today I tried an idea from Andrew Morrison (blog, Twitter), which appeared in the November issue of The Physics Teacher: Single Sentence Labs. Andrew writes, “a truly authentic scientific experiment does not come with any instructions.”

So as an introduction to our unit on acceleration, students were given this single-sentence lab: Does a spring rolling down an inclined lab table speed up? Justify your claim with evidence and reasoning.

It was fantastic. Lots of discussion within and between groups about possible experimental designs and analysis.

Some students went the traditional stopwatch and meter stick route:

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Others asked for motion detectors:

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One group did video analysis:

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On Friday, we’ll share our experiments and results.

NOTE: Last year, I did something similar, but used batteries instead of springs. Since the springs are hollow, they have a larger rotational inertia and accelerate more slowly than batteries. It takes about 5 seconds for the springs to travel the length of the 6 foot lab tables at a slight incline (about 3 volumes of Conceptual Physics texts high). I assume PVC pipe cut to pencil length would work well, too.

NGSS Science and Engineering Practices:
#3. Planning and carrying out investigations
#4. Analyzing and interpreting data
#5. Using mathematics and computational thinking
#7. Engaging in argument from evidence

##CAPM

Day 57: Balanced Force Lab Practical

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College-Prep Physics: Today we did a balanced force lab practical to tie together all our work on forces. It’s similar to the ones I’ve written about in past years. However, this year we used the green buggies and whiteboards instead of wood blocks and carpet/rubber. (This is because this year, in previous labs, some groups already worked with wood blocks and carpet/rubber.)

Given only a green buggy, a whiteboard, a spring, a 200-gram mass, and a ruler:

  1. Determine the spring constant of your spring.
  2. Determine the weight of your green buggy.
  3. Determine the force of kinetic friction between your buggy’s rubber tires and your whiteboard.
  4. Determine the coefficient of kinetic friction between your buggy’s rubber tires and your whiteboard.
  5. Predict the force of kinetic friction when 500 grams is added to your buggy. Have your teacher test your prediction!

UPDATE 2014 DEC 3: We found that when the 500 gram mass is added to buggy, the buggy rolls (rather than slide) when pulled. A binder clip on a rear wheel works great to lock the wheels so the buggy slides.

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NGSS Science and Engineering Practices:
#2. Developing and using models
#3. Planning and carrying out investigations
#4. Analyzing and interpreting data
#5. Using mathematics and computational thinking

##BFPM

Day 54: Kinetic Friction

College-Prep Physics: Last Thursday, students investigated the factors that might affect kinetic friction and how kinetic friction compares to static friction.

2015 CP 02 BFPM (1)

Today, students looked at the relationship between normal force and kinetic friction. Is the relationship proportional, like our previous experiments with static friction? If so, how do the slopes for kinetic friction compare to that from our static friction experiment?

2015 CP 02 BFPM (2)

NGSS Science and Engineering Practices:
#2. Developing and using models
#3. Planning and carrying out investigations
#4. Analyzing and interpreting data
#5. Using mathematics and computational thinking

Day 48: Pull-Back Truck Lab

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College-Prep Physics: Today students designed their own labs using pull-back toy trucks. They formulated their own question, designed their own procedures, collected data, and analyzed it. The one stipulation was that both the independent and dependent variable must be quantifiable because they are developing a specific mathematical model for their data. Later they will be presenting their results on mini-posters and sharing with the class.

NGSS Science and Engineering Practices:
#1. Asking questions and defining problems
#2. Developing and using models
#3. Planning and carrying out investigations
#4. Analyzing and interpreting data
#5. Using mathematics and computational thinking

Day 40: Factors Affecting Friction

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College-Prep Physics: First, we brainstormed possible factors that might affect the maximum strength of static friction between two surfaces. Then students designed their own experiments to determine which of those factors actually mattered. Finally, we tried to use our “interlocking bristles” model to explain our results.

— Weight/mass: Definitely affected friction. Why? The bristles interlocked more, making it tougher for them to slide past each other. This is easily demonstrated and felt using toothbrushes.

— Surface Area: Surprisingly, this did NOT matter (with the exception of groups that used highly irregular surfaces like carpet, felt, and cork). Why? Well, a larger surface area means more bristles in contact, which should mean more friction. But a larger surface area also means the surfaces are less compressed, which would reduce the the friction. This is easily demonstrated with weights and foam.

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So the net effect is no change in friction.

— Surface material: Changing the material of either surface also affected the maximum amount of static friction between the surfaces. This is similar to changing the material and arrangement of the toothbrush bristles.

##BFPM

NGSS Science and Engineering Practices
#2. Developing and using models

#3. Planning and carrying out investigations