Is "support force" a "true force"? it seems incompatibe with F=ma For example if a box is sitting on a table, not moving, it is said that the table exerts a support force on the box. But the box and the table are both inertial right? so if F = ma (force = mass x acceleration) and acceleration is defined as the rate of change of velocity, and velocity is defined as the rate of change of position of an object, but the table is stationary, then how could there be any velocity? and if there's no velocity than how is there any acceleration? and if there's no acceleration than how can there be any force? ( m * 0 = 0 ). Would it be proper to say that the table has no net force, if so could it still have a supportive force? is supportive force a real force in terms of F = ma or is it a not a "true force" sort of in the way centrifugal force is not a "true force"?