Question

Consider a gliding seed similar to that of Alsomitra macrocarpa (Fig. 12.11a, also p. 261). The seed has a mass of 250 mg., a functional lift-to-drag ratio of 4.0, a lift coefficient under the same conditions of 0.3, and a wing area of 5000 mm^2. The seed is released 15 m above the ground and reaches its final velocity essentially immediately. a. In still air, what is the greatest horizontal distance it can go from the point of release? b. How long will it take to hit the ground? c. If the seed is released into a temporally steady, spatially uniform, horizontal wind of 5 m s-1, how far will it go, (i) gliding with the wind, and (ii) gliding into the wind? d. In still air, the velocity along the glide path is about?

Answer 1

a) The greatest horizontal distance is, 4 -(Lift to drag ratio) d = hx(Lift to drag ratio) d-(15m)x4 d 60m b) The time take to hit the ground is, 9.8 t = 1.75 s c) The required di stance the glide will ge is, s ut (5m/s) (1.75 s) s 8.75 m d) The required velocity in still air is, v-ugt (5)+(9.8x1.75) v 22.15 m/s