# Day 92: Circular Force Diagrams and Motion Pillars take 2

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

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.

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

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.

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:

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.