Newton’s Second Law and Physics Textbooks

Abstract Contemporary textbooks of general physics teach us that the second law of Newton is F = ma . However, historical research has shown that Newton never wrote the equation, that Euler announced that he had discovered F = ma as a new principle of mechanics, and that Newton's second law and F = ma are different. This paper looks at the question from a different angle, namely how the principles have been applied to problem solving. To do this, we examine the problem-solving strategies used in the eighteenth century, in the following two centuries, and in textbooks today. We find that eighteenth century authors, namely those who followed Newton, did not use F = ma . In the nineteenth century, the equation became important in the practice of mechanics, as well as for conceptual purposes, physicists were concerned with the concept of force. These physicists did not identify the equation with Newton's second law. By comparing the problem-solving strategies of the eighteenth century and today, we can clarify the concept of force and understand why solving the conceptual problem of force has been difficult.