*40%*:**Improving students’ understanding of quantum measurement. II. Development of research-based learning tools***37%*:**Systematic study of student understanding of the relationships between the directions of force, velocity, and acceleration in one dimension***37%*:**Testing Students’ Understanding of Vector Concepts***36%*:**Algebra-Based Students & Vectors: Assessing Physical Understanding in Arrow vs ijk***35%*:**Test of understanding of vectors: A reliable multiple-choice vector concept test***35%*:**Initial understanding of vector concepts among students in introductory physics courses***35%*:**Students’ Understanding of the Concepts of Vector Components and Vector Products***34%*:**Modular Approach to Physics: Average Speed versus Average Velocity***34%*:**Helping students develop an understanding of Archimedes' principle. II. Development of research-based instructional materials***34%*:**A Research-Based Approach to Assessing Student Learning Issues in Upper-Division Electricity & Magnetism***34%*:**How do students in an innovative principle-based mechanics course understand energy concepts?***34%*:**A summary of research-based assessment of students' beliefs about the nature of experimental physics***33%*:**Improving Student Understanding of Vector Fields in Junior-Level E&M***33%*:**Improving student understanding of Dirac notation by using analogical reasoning in the context of a three-dimensional vector space***31%*:**Improving Students' Conceptual Understanding of Conductors and Insulators***31%*:**Investigation of Students’ Preconceptions and Difficulties with the Vector Direction Concept at a Mexican University***31%*:**Students' difficulties with unit vectors and scalar multiplication of a vector***31%*:**Tracker Video Analysis: Remote Control Helicopter***30%*:**Discipline-Based Education Research: Understanding and Improving Learning in Undergraduate Science and Engineering**