Advanced Physics:
We briefly discussed the answers to the Ranking Task I handed out yesterday. Here it is:Unit 6 Ranking Task-The Merry Go Round –All Questions
Most of the students did very well on it. In regards to the last question, I asked a series of questions aimed at gauging if the students understood a key concept about uniform circular motion and radial force. Here it is:
Me: What is acting as the radial force in this example.
Ss: The static frictional force.
Me: Good, which rider, D or F has a greater static fictional force?
Ss: They have the same static frictional force because they have the same mass and the we an assume he same coefficient of friction.
Me: Good. I see you have Rider D with a greater radial force than Rider C. Why is that?
SS: Ummm…. well….. let’s see…..
OK, it was not really like that for the last response, but it did take a bit of time for the classes recall that there is a difference between a required radial force and whether or not the force supplying it is larger enough. I used an analogy. Let’s say I go to Starbucks and I want a coffee that costs $3. I have some dollars in my pocket, but just because I have some dollars that does not necessarily mean that I have enough dollars. I have to actually check to see if I have enough. If I have $4, I’m good to go, but if I have only $2, I don’t have enough and I get no coffee.
They students worked on 7 problems in class in small groups. No group finished all 7, so (by design) they will have some to work independently on. I suggested which ones were more challenging that they should work with their partners on. This type of approach (in class time to work) is a bit new to me, I usually do not allow extended periods of time for this. I don’t think it is a bad thing, I just want my students to realize they will have to do some independent work too.
To see which problems they want to see presented tomorrow, I set up a Schooloogy poll. The one(s) with the most votes are the ones we’ll go through. Here is a screen shot of it.
General Physics:
Today was about throwing numbers into the net fore equations we have been writing as we draw force diagrams. I gave them a series of situations, they solved for the tension force, then we checked it:
Sample Tension Force Problems #2
Even though it is hard to read, the last problem set the students up to do a static equilibrium challenge tomorrow. Here is a better picture of the last problem:
They were given one of the tension forces (measured by the WDSS) and an angle. Tomorrows problem is very similar, but with both strings angled.
