Day 52 – Hooke’s Law Lab

WP_20161121_09_52_16_Pro.jpgPhysics 11 – Students conducted a lab on Hooke’s Law today.  They were prompted to model the relationship between an external force and how it affects a spring it is acting on.  Data collection went pretty well and I strongly suggested that students use Excel to produce their graphs. Several groups opted to hand graph their data, which was very surprising to me. However, after pointing out a few things that they could do to improve their graphs, most of these groups eventually realized that re-doing it in Excel would be a lot of faster and probably more accurate.


Day 51 – Discounts

Math 8 – Today the class worked on the above problem. Lots of groups had problems with it, and couldn’t move off the idea that 30% + 45% + 25% = 100%. They couldn’t think of any other thing to do with the numbers.


There was also some nasty misconceptions with adding fractions! Lots of kids did 45/100 + 25/100 + 30/100 = 100/300.

By the third class of math 8 I finally found out what I had to do as a teacher to get the students on the right track. First, I had to make sure that the problem doesn’t turn into a money issue. If students equate the discount to saving money, there will be trouble. Keep the problem centered on saving gas, because everyone agrees that you can’t have a car drive without using fuel. Secondly, I had to really listen carefully to what the students say and really jump in when they say something like “45% of 70”. A ha! What operation is associated with the word “of”? That’s right, multiplication, not addition…


The neat thing about this problem, after I’ve done the good things needed to pull it off, is how engaged the students get. They can taste how close they are to a solution and want to solve it.  It was Friday afternoon, the dismissal bell had gone, and I had several kids sticking around to finish their work.

Day 50 – Misconceptions of Gravity

3 particles.PNG
Physics 11 – Today was our Misconceptions in Gravity class. We did a lot of voting and discussion centered on three themes: what things affect gravity?, do small things also have a force of gravity?, and do interacting objects have an equal force of gravity acting on each other?.

There’s too much on these subject to list here, but the above diagram is one of the more convincing arguments. Students see that as they add additional particles to the diagram (X, Y, Z, etc), each new particle has a force of gravity acting between it and A. The extension of this is that large objects, or objects with millions or billions of particles, will have the same number of force arrows as does the small object (A).

Some students were a bit too “white flag-ish” for this class.  It’s so easy to tune out and say to yourself “I don’t know.”  Those students can make this a difficult lesson to teach. But other students really like it. It’s interesting and challenging.  It’s solving a mystery or a puzzle.

Day 49 – Self Assessment

Math 8 – Students check over their answers with my answer key and also did a good job of correcting my answer key. I’m always honest about my ability to make mistakes. I think this is a good thing, up to a point. We still have to model good habits, hard work to get to a correct answer, and an appreciation of doing good work.

And no, I’m not going to collect 85 sheets of work and put a bunch of checkmarks on them, or give them marks. I do give out a lot of feedback as I walk around the class for 60 minutes. I do believe that custom feedback would be better but I don’t have time for it, and research shows that written feedback is most often ignored by students.

Day 47 – Specialize for Problem Solving

Math 8 – Today I am trying to get kids to extend their practice of using concrete examples and specialization for general math problem solving. The above picture was one example we did. Many students didn’t know how to approach this problem initially but they were able to re-frame it with a question they could do: they realized that 50% of 1480 is 740. This helps them figure out a method for doing the problem they really want an answer to.