# 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.