This is what he has to say when students tell him they just don't understand physics.
This is something I often hear students say around the midterm. The truth is that no one “just understands” physics. No. Instead, physics is the result of a battle. There is battle in your head between common ideas and new ideas. There is a struggle in your mind and on your paper about finding a strategy to solve a problem.
You can’t just “get physics” by going to class. Understanding in physics only comes (for just about all of us) through sweat and tears. You have to do the homework. You have to go to class. You have to read the textbook. This isn’t drive-thru learning. If you aren’t putting in the time, you are going to make progress.
This is similar to what I've said all along on here, that you just can't sit and read a book on physics and hope to understand it. What you may have understood is something superficial. The only way to grasp the knowledge is by solving a bunch of problems, making mistakes, and learning from them. That is the only way to get a feel of the essence of what you are learning. I've always used the analogy of learning how to ride a bicycle. You can read and hear people tell you how to ride a bike till you're blue, but you'll never acquire the skill to ride it till you actually sit on a bike and practice, practice, practice. You will fall a few times, get a few scrapes and bruises, before you finally get it.
The same thing with understanding physics.