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Figure 6


Fig. 6. Force diagram for unsteady (accelerating) glides. The resultant aerodynamic force is inclined forward because of the horizontal acceleration. A downward acceleration indicates that the vertical component of the resultant aerodynamic force has a smaller magnitude than the weight. M, mass of the animal; g, acceleration due to gravity; R, resultant aerodynamic force vector; L, lift; D, drag; {varphi}, reference angle between negative velocity (drag) and resultant aerodynamic force vector.