# Day 98: Survey Says…..

As part of the Educator Effectiveness project, we are required to survey the same set of students, twice during the course in which we instruct them.  So, today before WB’ing the results of the radial acceleration experiment, I ask the Advanced students to complete the second survey.  It has to be the same set of questions we gave before.  There are 10 or 12 questions we must ask and can not edit, and we are allowed to give more.  I used a google form again because I really like how the results can be displayed.  There are always some interesting stats that pop out at me. For example:  2 students (of 66) disagree or strongly disagree that I am knowledgeable about the subject I teach, a total of 6 students disagree or strongly disagree or don’t know if the lessons I plan are engaging.  I did learn that I have something to really work on… allowing students to demonstrate knowledge in a variety of ways (21% disagree, strongly disagree or don’t know).  This will be something I will try to work on throughout the rest of this year and into next year.  Any ideas on alternative assessments would be appreciated.

We WB’ed the radial acceleration experiment.  Next year I will alter how I do this… probably have the students pick a radius and monitor the radial acceleration as the angular velocity is varied.  I have not done that in the past because I have always felt that if students look up the equation for radial (or centripetal acceleration) they will see ar=vt^2/r.

We also started a sample problem.  Here is a clip of it.

The students will have the mass, the angle with the horizontal, and the length of the string.  We are going to solve for the time it takes to complete 10 revolutions, then check it of course.

General Physics:

More force diagram whiteboarding.  At the close of the hour I asked the student’s to provide me with their color. Most students in my 4th mod class were yellow (needing more practice) and in 7th most were green.  So tomorrow, with Mod 4, we will do some small group work (groups based on color) and in7th, we might play the mistake game as described by Kelly O’Shea here.

# Day 67: Force Diagrams and Solving ca Problems Graphically

Today (and probably tomorrow)was spent WB’ing a set of force diagrams.  We only made it through 3 or 4 of the eight I assigned.  It took long for a few reasons. First of all, not all the students completed the  practice (which really does not make me happy… I have not found a way to convince some of them that the MUST do the practice when they do not understand the topic) so there were many questions as they prepped the WB’s.  Second of all, it takes them a bit to explain the diagram and answer the audience questions.  Finally, I always ask a few extra questions that require some extra explanation.  For example, on this one:

I asked how the tension forces would change if everything was the same (so still the same angle) EXCEPT the right side string was attached to a ceiling that was higher so the string was longer.  Or if the angle was different.  We then use equipment to set up the new scenario and record the forces.

Here is another example:

I ask what would happen to each of the three forces (Fg, Fn, and Ft) if the ramp were made steeper.  To demonstrate this I use a set-up shared a number of years back by Dale Basler at a Phox Share group meeting.  It’s a bit hard to describe, but it uses the WDSS as the box and the 3-axis accelerometer.  Each one is displayed using an animated vector representing  one of the forces.  Fg is the y-axis that is calibrated to -9.8m/s/s; the Ft is the  x-axis and the Fn is the x-axis. It’s all wrapped up in a pretty like Logger Pro file, but here is a picture of the set-up:

So as the right side is elevated, the animated vectors show that Fg does not change, but the Ft and the Fn do.

General Physics:

We discussed the kinematic graph assessment they took on Friday and then started WB’ing the graphical solutions to some constant acceleration problems.  Tomorrow there will be more of the same.