*94%*:**Improving student understanding of addition of angular momentum in quantum mechanics***69%*:**Student understanding of the angular momentum of classical particles***61%*:**Improving Students' Understanding of Quantum Mechanics***57%*:**Studentsâ€™ Understanding of Stern Gerlach Experiment***57%*:**Improving Studentsâ€™ Understanding of Quantum Measurement***54%*:**Improving studentsâ€™ understanding of quantum measurement. II. Development of research-based learning tools***53%*:**Improving Students' Understanding of Lock-In Amplifiers***51%*:**Investigating student understanding of basic quantum mechanics in the context of time-dependent perturbation theory***48%*:**The Influence of Student Understanding of Classical Physics When Learning Quantum Mechanics***48%*:**Assessing and improving student understanding of quantum mechanics***48%*:**Student understanding of basic probability concepts in an upper-division thermal physics course***47%*:**Student understanding of the ideal gas law, Part I: A macroscopic perspective***47%*:**Student understanding of static equilibrium: Predicting and accounting for balancing***45%*:**A hierarchical model of the development of student understanding of momentum***45%*:**Student understanding of the work-energy and impulse-momentum theorems***45%*:**Investigating Student Understanding for a Statistical Analysis of Two Thermally Interacting Solids***45%*:**Upper-division student understanding of Coulomb's law: Difficulties with continuous charge distributions***43%*:**Helping students develop an understanding of Archimedes' principle. I. Research on student understanding***43%*:**Student Difficulties in Understanding Probability in Quantum Mechanics**