Physics is a broad range of topics. Some students can grasp pretty quickly while others are more difficult. I have found that topics around force and motion are ones that stump some students. Newton's laws are particularly difficult for students. I believe that part of the reason is that these laws are complex and it is hard to bring them down to a middle school level without introducing misconceptions. I don't know what the solution is, but I'm going to keep trying to present these topics to my students in new and different ways. One way is these short video clips that I found. There are shot clips around 3 minutes long and come with a short quiz at the end.
What struggles do you have teaching physics to your students?