Day 141: Harry Potter Visits NHS (or an intro to electrostatics)

Advanced Physics:

Yeah, I know it is a pretty big jump…. from the momentum model (including impulse) to electrostatics. I’ve never been really pleased, but have never taken the jump to put momentum in somewhere else.  I guess just more to ponder.  Anyway, today we white-boarded ‘The 7 Charge Questions’.  It is a worksheet I out together to build the essential aspects of charge. It’s nothing fancy mind you.  It just gets across the info I want the students to understand about charge (symbol,units), how objects get charged (friction, conduction, induction), how objects get uncharged (grounding), that there are only 2 types of charge (+ and -), how charged objects interact (likes repel, opposites attract, and that implies a force is exerted between the objects, that charge is mobile and can be transferred (both + and -), oh yeah, and what polarization is.  All of this helps us form a model of what and how it behaves.

It’s interesting that many students just want to define charge as being when thee are more or less electrons.  But then I ask them what an electron is.  They politely regurgitate ‘a negatively charged particle’.  But wait… charge is when there is more or less charged particles?  Then they see there is a bit more to it.

After discussing for a while, we finally do a demonstration to bring many of the aspects of the charge model together:

What you do not see is the way I introduced it… I did the demo first, dressed with Harry Potter glasses and a cape.  The Harry Potter Halloween theme was playing on repeat the entire time.

VIDEO DISCLAIMER: The young lady in the last clip is from two years ago.. it’s just a nice longer clip and she is an awesome daughter (err, I mean  student).

For the next class, the students were given a practice sheet. Again, nothing too incredible, but they do have to draw a series (at least three) diagrams to illustrate the process of induction and the process of conduction.  In the next class meeting, they will also have an opportunity to demonstrate mastery by charging an electroscope using induction or conduction.

General Physics:

This class period was spent white-boarding a series of COE problems.  I also used it as an opportunity to do two things. (1) Ask some conceptual questions about the given situation (if the mass had been twice as large…), and (2) show them the power of substituting equations FIRST before putting values in.  For example: Screen Shot 2015-04-19 at 9.30.16 PM

In this case, Eelas = Eg.  So rather than solving for elastic energy, then setting it equal to the gravitational, then using that value to solve for the height., simply substitute in the equations:  1/2kΔx^2 = mgh, now solve for h.  Using this approach makes it soooooo much easier to answer the conceptual questions like what is the mass had been twice as large….

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Day 118: COE WB’ing and Sledding

Advanced Physics:

Today we WB’ed four of the six problems I had assigned last night.  I choose one problem (a pogo stick problem because I have a pogo stick a class several years back all chipped in to get me) and I let them choose 3 of the remaining 5 to complete. I like these days because it gives us a chance to practice some conceptual questions.  For example, one of the problems was a spring launching a mass vertically, I know you all know the problem.  I asked about what effect doubling the spring constant would have on the maximum height… or the ‘take off’ velocity.  I also asked them to predict the shape of a graph of height as a function of compression of the spring.  If I had thought about it earlier, I would have had a Logger Pro graph waiting on the wings.. or better yet a Vpython (or Glowscript) or even Excel spreadsheet with slider bars.  Well, there is always next year!

 

General Physics:

Today we went sledding.  We used the LabQuest2 (well the x-accelerometer) to measure the acceleration as the students rode down the hill. There are a few things I had not thought about ahead of time.  First of all was the fact that some kids did some spinning, also that it would be measuring the acceleration once the kids were on the horizontal part.  Hopefully the were able to get some meaningful data.  I did not really have a chance to look, I was serving up the Hot Chocolate!

Day 117: Are you kidding? It’s that easy? and The Sledder Lab

Advanced Physics:

Today we summarized the four main energy models; Eelas, Ek, Eg, and Ediss. After this we finally looked at two COE sample problems.  The first one was this:

Screen Shot 2015-02-18 at 9.41.15 PM

It was the same problem I gave the students to introduce the energy unit.  At the time, they solved it (or attempted to) with kinematics and dynamics.  It is about 15 steps to get it done.  I mentioned at the time, we could probably do it in in 2 or 3 steps.  So today was the day to show them that.  They caught on right away… decide your initial and final situations, draw the energy bars so you can write the energy equation, then solve.  For this problem it is Eg (initial) = Ediss (final).  From there I STRONGLY suggested they use substitution… that COE equation boils down to h=μk*Δd.  (There is another step in this, it is to use theΔd and the 70cm rough patch length to find the final resting spot, but that was not thee important part of the lesson.)

In many of the classes I heard comments like the title of the post and that’s actually pretty cool.  One of the reasons I like substitution is that it really helps kids with conceptual questiions like… what happens to the distance is slides if I double the mass?  Well, nothing, mass cancels out.

The second problem was predicting the velocity of a pendulum at the bottom of it’s swing.  This one is equally simple and then we actually check it with a bowling ball pendulum hanging from the ceiling.  We use a Vernier ‘laser-gate’ with one gate timing to check the prediction.  It’s typically very close, but smaller, because there is a tiny bit f energy dissipated.  It provides a chance for us to do this demo:

 

 

General Physics:

We discussed the N2L assessment the students took yesterday, then did a fair amount of discussion to get ready for the ‘deployment’ activity.  The assessment was a sledder on a frictionless hill, not realistic at all, because there IS friction.  The goal of the experiment is to determine the coefficient of friction for a sled and the snow.  Yep, we’re going sledding tomorrow.

Through the course of the discussion, we see that we need the angle of the hill,  the combined mass of the sledder and sled, and the acceleration.  To determine the acceleration, we ill be using the LabQuest2 x-accelerometer.  It was absolutely incredible today using the LabQuest Viewer software and our wifi network to show hte students how to set-up and use the LabQuest2.   Way to go Vernier, as always, you guys ROCK.