What is the standard symbol for force in Newton's second-law equation? F.
The standard equation is F = ma, where F represents force, m represents mass, and a represents acceleration. More precisely, the bold or arrowed form, F⃗ = m a⃗, indicates that force and acceleration are vectors with both magnitude and direction.
In a more general formulation, Newton's second law is F⃗ = d p⃗/dt: the net force equals the rate of change of momentum. The familiar F = ma follows when the object's mass is constant. The symbol F is conventionally associated with the English word “force,” although mathematical notation itself is an international shorthand.
A frequent mistake is to read F as one individual force when the equation describes the net or resultant force. Several forces—gravity, friction, tension, and a push, for example—may act simultaneously, and their vector sum is the quantity represented by F. Force is measured in newtons, with 1 N equal to 1 kg·m/s².