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16 January 2018

Trust the Process

I had a rough class Tuesday.

I thought about changing course.  I didn't - I kept plunging forward.  And everything worked out beautifully.

We were working on the direction of force and motion using these in-class lab exercises.   I encourage you to take a look.  They involve three situations:

1. Jumping on or off a force plate
2. A hanging object attached to a cart
3. A fan cart attached to a hanging mass over a pulley

In each case, two forces act on an object.  Students are asked to determine the direction of acceleration, and then which of the two forces is larger.  Finally, they go to the back of the room where I have equipment set up.  They use force probes and plates to verify their predictions.  Nothing here is quantitative - we don't predict a value for the tension in a rope.  In this exercise, we only are comparing which of two forces is larger.

Sounds easy enough, right?  "The object moves up and slows down, so acceleration is downward.  Net force is also downward.  That means down forces are bigger than up forces, so the weight is bigger than the tension in the rope."

Hah.  No, on Tuesday I kept hearing "In order for the object to move upward there must be more forces pulling than pushing upward than downward.  And the object has weight, so the tension in the rope is massive.  Plus here are three more sentences full of nonsense please count it right."  I'm barely making this up.  My class was getting palpably frustrated.

In 80 minutes of lab work, about half the class completed one exercise; the other half completed zero.  I had a major assessment scheduled for the last part of Thursday's 90 minute class.  Would the students be ready?  Should I reschedule?  Should I stop the lab work and start just doing problems in front of the class to assuage their frustration?

It's hardly ever a good idea to slow the pace of the class just because students seem to struggle the first time seeing a difficult concept.  If Newton's second law were easy, I wouldn't be employed. Doing problems in front of the class doesn't help anyone - the only way to learn physics is to make mistakes, then to learn from those mistakes.  Students must be active, not passive, otherwise they'll make the same mistakes on the assessment that they were making in class.

So I pushed on.  Thursday's class began with a brief quiz, followed by five minutes of discussion about the problem set.  Then back to lab work for 45 minutes before the major assessment.  I braced myself...

The pace of work ascended to the next available energy level.  Everyone finished at least two exercises.  About half the class finished three.  And scores on the major assessment were as high or higher than ever.

Trust the process.  When you're doing creative lab work, or any sort of physics teaching that isn't just you telling students how to do problems, frustration and wrong answers are a natural part of the learning process.  Let that frustration happen.  Keep morale up as best you can.  Because the epiphany will come.

And what of the two or three students who didn't perform well on the assessment?  Wouldn't they have been better served by a different approach?  Perhaps, but not likely.  In any case, their epiphany will come, too.  In fact, during the next Monday's test corrections class, one of these three poor performers looked at me with a wry smile.  He said, "you know, I kept making dumb mistakes.  I should have known these answers, they seem really easy now.  I'll get these next time no problem." 


  1. Convincing first year students and parents that learning physics is a process is very difficult. Even sharing concerns about this with other non physics teachers is not always helpful or reassuring. This is my 11th year teaching and I admit I still second guess myself and the processes. Two years ago I redesigned my course to loop concepts throughout the year. It has worked very well. I often get the "why didn't I get this earlier" comment during the second semester. Here is the order for my fist year Pre IB Physics class.
    Linear Motion and Newton's laws (1D motion and forces only),
    Work and Energy Conservation,
    Circular Motion and Gravitation,
    Electrostatics, Circuits and Magnetism,
    Impulse and Momentum,
    2D Vectors and Projection,
    Static and Dynamic Fluids.
    This has allowed me to loop concepts and questions much easier throughout the year, and helps ensure my promise of "don't worry, you'll get it next time because you will see it again".

    Thanks for all the insightful posts Greg. I am a better educator because of what you share.

  2. I really love this “loop” as the thrust of your process. That gives you something tangible to tell students and parents - not just “trust me, you’ll catch up” but “...and here exactly when you’ll catch up, and why I know you will.” Awesome.

  3. I, too, have become a better educator as a result of your sharing and help. I think I'm going to put this on the wall in my classroom - "Trust the process" because it is so true and so necessary, for me and for the students.
    The loop idea is something that in my opinion for AP is served with rotational motion. It covers all the major topics again as the end of the course is nearing - kinematics, forces, momentum, and energy. I'm curious as to whether these exercises were for your conceptual physics class or for your AP?

  4. Thanks for the kind words, Jessica. These exercises were for conceptual physics.