Day 92: Circular Force Diagrams and Motion Pillars take 2

Advanced Physics:

Today we discussed the rotational kinematics assessment the kids took on Friday.  It continues to amaze me that even after a full semester with me, most of my students still reach for the equations….Here is  problem I gave them on the assessment

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It is REALLY easy to solve with an angular velocity-time graph, but tougher and longer with the equations… sigh.

We also looked at sample tangential velocity problem I asked the students work on over the weekend.

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That’s a picture of some wind turbines all my students have seen many, many times.   I asked them to determine the speed in miles/hour for the tip of the blade.  I provided them with the pdf of the design specs. The blade length is 134 ft and the operational rate is 14.4 rev/min….. the answer surprises most  138mi/hr.


After that we developed the concept of radial (or centripetal) acceleration.  I prefer radial because they are less likely to confuse it with centrifugal AND we hit a vertical circle we can discuss a tangential acceleration more easily.


General Physics:

We WB’ed the same set of motion pillars we used with the Advanced class.  I had 3 groups CYOP (create your own problem). One I used as an exit formative assessment, the other twoI will use as additional formative assessments.  We also just briefly started discussing how to draw force diagrams.  More on this tomorrow.

Day 65: N1L including the Giant Hovercraft of Physics

Advanced Physics:

In the first part of class we looked at some examples of Newton’s 1st Law.  I did a few classic N1L (inertia) demo’s.  I’m sure most of you have seen this one:

I also had the students get involved.  I made  I ‘heart’ Physics book markers the students could earn by getting it out from underneath the dry erase marker without touching or disturbing the marker.  Sort of a mini version of the table cloth demo.

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After that, they rode our giant hovercraft of physics (sorry, no photos).

We also did a bit of WB’ing on a practice sheet that made use of  motion pillars.  Here is an example:

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We did not quite finish, so that is where we will pick up tomorrow.


General Physics:

We finished the phan cart predictions and continued to practice solving constant acceleration problems with a v-t graph.  As of yet, the generals have no kinematic equations for constant acceleration.