Rotation around a fixed axis the same mass and velocity of rotation. Like linear momentum, angular momentum is vector quantity, and its conservation implies that the direction of the spin axis tends to remain unchanged. For this reason, the spinning top remains upright whereas a stationary one falls over immediately. The angular momentum equation can be used to relate the moment of the resultant force on a body about an axis (sometimes called torque), and the rate of rotation about that axis. Torque and angular momentum are related according to just as F = "d"p/"dt" in linear dynamics. In the absence of an external torque,
Mass flow rate ejecting spent fuel. Often, descriptions of such objects erroneously invoke Newton's second law F =d("m"v)/d"t" by treating both the mass "m" and the velocity v as time-dependent and then applying the derivative product rule. A correct description of such an object requires the application of Newton's second law to the entire, constant-mass system consisting of both the object and its ejected mass. In hydrodynamics, mass flow rate is the rate of flow of mass. In electricity, the rate of flow of charge is electric current. Mass flow rate In physics and engineering, mass flow rate is the mass of a