STACK for a Physics Textbook

Physics Curriculum & Instruction

David Hilsen


The commercial textbook publisher, Physics Curriculum & Instruction have developed STACK questions to accompany a Physics textbook [1]. These make significant use of random variants and intermediate problem-solving steps. It was important to have feedback on problem design from academic colleagues, and to have support for significant figures and scientific units in STACK. The question bank will contain 3500 questions by the start of the 2019/20 school year.


Physics Curriculum & Instruction is a Minnesota-based company providing schools with learning resources for Physics. With a lot of open-source options becoming available, putting resources into developing a commercial textbook can carry a significant risk. Physics Curriculum hopes to address this by directing their development efforts towards online physics educational resources. It was important to have a system that allowed them to address the wide variety of needs of instructors and that utilised randomization of numerical values. This makes it nearly impossible to search online for the answer to a particular problem; a major concern for publishers.


Three forces are displayed as vectors. The student must find the magnitude and direction of the sum of the three forces.
Figure: A Physics Curriculum question involving intermediate problem-solving steps.

A large collection of online STACK questions were developed to accompany the book Physics Fundamentals [1]. Access to the online homework package can be purchased along with the book for an extra fee. The online questions are managed in the online learning environment Physics LE, which runs on Moodle. Moodle was picked for its Enrolment key feature and its Adaptive mode question behaviour that allows students to make multiple question attempts with immediate feedback.

The team had four people authoring STACK questions, and two additional people working on Moodle and the cloud servers. Authoring questions required an average of just over one hour per question with a significant portion of that time devoted to quality control and testing. Ultimately the development sums to a significant financial investment, but also one that leaves an end product of high quality.

A significant focus in the authoring of questions was on intermediate problem-solving steps, and which ones would be most beneficial to help the student formulate a problem-solving strategy. It was important to go beyond a system in which students simply enters a final numerical value that is marked right or wrong with no additional feedback. The intermediate problem-solving steps used are of the following type:

  1. multiple-choice questions, using text or diagrams, checking for understanding and problem-solving approach,
  2. input of relevant equations or algebraic expressions,
  3. input of intermediate numerical values which need to be calculated to obtain the final answer.


The service went live in January 2019. Since then, 15 schools, both high schools and colleges, have urchased the online question package. Instructors gave positive feedback, especially appreciating the multiple-part question structure where students are given specific feedback.


A question about a pole-vaulter beginning a jump with a running start, then rotating his body about the other end. Students must give an expression for the speed.
Figure: A Physics Curriculum question involving potential energy.

Initially, there was no provision in STACK for handling significant figures, and limited support for physical units. This was a big barrier for Physics question authoring, and hence a more robust system was developed for this purpose. Additionally, high school students sometimes struggle with the syntax for equation input, especially those with minimal computer background. This continues to improve within STACK and may not be a concern in the future.


Instructors and colleagues provided feedback from an outside perspective indicating where students might have difficulty. This encouraged the authoring of additional PRT nodes, for example checking for a particular misconception.

What's Next?

There are many additional schools evaluating the Physics Curriculum online homework system, and additional schools are expected to join. Furthermore, the question bank continues to grow. By the start of the 2019/20 school year, Physics Curriculum plans to have 3500 STACK problems in their system, many of these multiple-part. There are also plans to partner up with OpenStax, a company producing high quality College Physics textbooks, to bring them an affordable online homework solution as well.


[1] V. P. Coletta. Physics Fundamentals. Physics Curriculum and Instruction Inc., Lakeville, Minessota, 2nd edition, 2010.