# Day 147: Charge Assessment and Work(ing)

Well it is the Monday after prom… ’nuff said’ right?  No surprise that most of my students became more sluggish as the day progressed.  So here is what we did.

The Advanced course took a ‘Charge Processes’ assessment.  I’m trying something new this year … rather than a summative test on charge; Coulomb’s Law, Electric fields and Electric Potential, I’m going to go with a few short assessments and skip the nitty gritty on how we transition from electric fields to electric potential.

SIDEBAR:  Part of the decision to do this is based on how far ‘behind’ I am from previous years.  We have lost sooooo may days for this, that and the mandated testing, that I am scrambling a bit to cover what I usually do.

Here is the assessment they took today.

Essentially it is straight out of Arons.  I really like it.  After the assessment, I allowed them to work in small groups to finish a practice set on Coulomb’s Law and then prep a WB for tomorrow.

General Physics:

Today we developed the model for work(ing).  I followed the same basic discussion approach I did with the advanced students I wrote about here.  The only real difference is that we do not talk about power right away.  It has been my experience that even though power is not a very difficult concept, sometimes piggy-backing the two concepts leads to confusion for these students.

# Day 119: Conceptualizing and Quantifying Work(ing)

We started the mod by taking another COE formative assessment.  Here is it:

Unfortunately, most the students did not correctly solve it.  There were two issues: (1) Silly errors (like canceling the 1/2’s) and using 20m as the final height, and (2) More f a conceptual issue, not including any initial kinetic energy, just starting with gravitational.  This surprised me a bit.  Some also went two distinct steps (very top to very bottom, the very bottom to the final height).

After the assessment, we WB’ed a sheet I put together a few years ago to graphically develop the models for work(ing) and power.  To conceptualize ‘when’ working is being done a system, we used the chairs the students sit in. Hold the chair at waist level, is there working being done ON the chair? (No, there is no displacement). Raise the chair up above  your head, now is working being done ON the chair? (Yes, the force is parallel to the displacement).

You get the idea. We also walked with the char at waist level, and pulled the chair across the floor. We used a WDSS as a force sensor to lift a 1.0kg mass above a motion detector (at constant speed) to build graphs of Force vs. displacement so the area trapped is the work(ing).  Then work(ing) as a function of time to build the concept of power (as the slope of the work vs time graph).

General Physics:

Today was strictly a work day. They finished analyzing the data gathered while sledding.  They also worked on creating their presentations that will be uploaded to Schoology in the form of a shared Discussion.

SIDEBAR: Interesting to note that last Friday was the last ‘sleddable’ day… it was nearly 50F here today.