Expert TA Blog

Classroom demonstrations can be a great way to get students excited about what you want them to learn, and in-class physics demonstrations can be easier than you realize. If you are not doing any in-class demonstrations, then you are doing too few. Here are some thoughts about getting started with demonstrations that are both affordable and effective.

1. Wow them! If you want to get students’ attention, show them something they aren’t expecting. Who doesn’t love a good trick by David Blaine or David Copperfield? There are plenty of physics experiments where the outcome is counterintuitive. When students guess one outcome and see another, not only does it grab their attention, but it also sparks interest in finding out why things behaved differently than they expected.

2. Classic examples of Counterintuitive Demonstrations: The two-part spool experiment is one that any instructor can do in class with minimal cost and minimal setup. All you need is a basic spool with rope or yarn on it. You can get a spool and rope at a home improvement store like Home Depot or a craft store like Michaels. It is important that the spool have an inner diameter that the rope is wrapped around. Simply put the spool on a tabletop, and ask the students which way the spool will roll when the rope is pulled horizontally. You can do this with the rope coming over the top of the spool and underneath the spool. The result will surprise some students. Here is a link to a video that shows this demonstration.

3. Sometimes a video can do the job. There are some nice experiments out there that involve set-ups that are either too complicated or too dangerous to do in the classroom. Dropping a tennis ball onto a basketball allows for the tennis ball to bounce back to a height much higher than its starting position (see a video here). You could probably do this demonstration in your class. However, if you want to include a golf ball, which goes to a height of about 27 feet when dropped from 3 feet, the demonstration probably becomes unsafe. If the golf ball rotates and is launched at an angle, rather than straight up, it could be directed at a student and cause injury. You can still get a reaction from your students when you show them the video. Ask them how high they think the top ball will reach and show them the video. If you really want to integrate the demo, go through all of the calculations together or get them started, and make it a group project.

4. Bullet block demonstration: For obvious reasons, it’s not possible to shoot bullets into wooden blocks in your classroom. This video demonstration shows a wooden block that flies into the air when hit in the center with a bullet. The demonstration will challenge your students with this question: When a block is shot off-center, will it fly higher, not as high, or the same height as the block that’s shot in the center? Again, the answer will surprise many. See the video here.

In 2015, the AP Physics Exam experienced significant changes. AP Physics B was split into two exams and two courses: AP Physics 1 and AP Physics 2. In addition, the amended approach emphasizes the processes of scientific inquiry and reasoning, experimental design and working symbolically. As shared in a previous Expert TA blog, the number of students who took the AP Physics exam doubled in 2015, but the percentage of students who scored a 3 or higher (and therefore received college credit) declined from 59.7% in 2014 to 39.2% in 2015. Examination of score distribution data from the College Board shows that the number one reason for the decline in passing scores in 2015 was lack of sufficient preparation for the free response questions.

Students are not getting enough practice with solving problems symbolically, which is a big part of the exam. In the free response section, test takers are asked to show all their work, and as stated in the course and exam description from The College Board, even correct answers may not receive full credit if supporting information is insufficient. This supporting information almost always includes fundamental symbolic relationships and equations. Preparation Material for the exams should not just require students to regularly deal with symbolic expressions, but should also continually reinforce the problem solving process. This gives students the opportunity to think about why a given equation is important within the context of a specific problem.

We believe that many homework platforms are not properly preparing students for exam day, because they simply ask a student to provide a final numeric value. However, to fully understand the material, and do well on the AP Physics exams, it’s important to know and show the process of arriving at the final answer. Based on our research, we see strong evidence that reinforcing the problem-solving process can have a significant impact on exam results for Physics students in college-level courses.

Our development of the Expert TA Online AP Physics I Study Guide is an effort to help AP Physics students receive the same practice that has guided students through rigorous Introductory Physics courses at the college level. In an effort to provide students with much needed practice, specifically using symbolic problem solving, we worked with AP Physics teachers to build modules for each of the key areas of the exam using our best symbolic problems. Additionally, Expert TA is not just for exam preparation, many high school teachers use Expert TA to assign homework in their courses. AP Physics teachers have the option to create weekly homework, quizzes, or tests, and allow their students to engage in guided practice through the study guide.