Drag equation by experiment. Of particular importance is the formula_8 dependence on flow velocity, meaning that fluid drag increases with the square of flow velocity. When flow velocity is doubled, for example, not only does the fluid strike with twice the flow velocity, but twice the mass of fluid strikes per second. Therefore, the change of momentum per second is multiplied by four. Force is equivalent to the change of momentum divided by time. This is in contrast with solid-on-solid friction, which generally has very little flow velocity dependence. The drag force can also be specified as, formula_9 where, "P" is pressure
Binary mass function the true orbital velocity is low (implying low mass objects) and the inclination high (the orbit is seen edge-on), or that the true velocity is high (implying high mass objects) but the inclination low (the orbit is seen face-on). The peak radial velocity formula_1 is the semi-amplitude of the radial velocity curve, as shown in the figure. The orbital period formula_2 is found from the periodicity in the radial velocity curve. These are the two observable quantities needed to calculate the binary mass function. The observed object of which the radial velocity can be measured is taken to be object