*45%*:**Vector Addition: Effect of the Context and Position of the Vectors***34%*:**Students' difficulties with unit vectors and scalar multiplication of a vector***33%*:**Vector Addition in Different Contexts***31%*:**Student difficulties with quantum states while translating state vectors in Dirac notation to wave functions in position and momentum representations***30%*:**Student Difficulties with Graphical Representations of Negative Values of Velocity***28%*:**Test of understanding of vectors: A reliable multiple-choice vector concept test***26%*:**Modular Approach to Physics: Vector Addition Practice - Three Vectors***25%*:**The effect of context on student's reasoning about forces***25%*:**Investigation of Studentsâ€™ Preconceptions and Difficulties with the Vector Direction Concept at a Mexican University***23%*:**Open-inquiry driven overcoming of epistemological difficulties in engineering undergraduates: A case study in the context of thermal science***23%*:**Students' Conceptual Knowledge of Energy and Momentum***23%*:**Studentsâ€™ Responses to Different Representations of a Vector Addition Question***23%*:**Students' Difficulties in Interpreting the Torque Vector in a Physical Situation***23%*:**Development and validation of a sequence of clicker questions for helping students learn addition of angular momentum in quantum mechanics***22%*:**A hierarchical model of the development of student understanding of momentum***22%*:**Improving student understanding of addition of angular momentum in quantum mechanics***22%*:**Student Difficulties with Trigonometric Vector Components Persist in Multiple Student Populations***22%*:**Improving student understanding of Dirac notation by using analogical reasoning in the context of a three-dimensional vector space***20%*:**Students' understanding of the addition of angular momentum**