The drag of a football is investigated in a water tunnel with a quarter-scale model and matching the full-scale Reynolds number. If the actual expected speed is assumed at 95 km/h, estimate the ratio of the drag force between the model and the full-size football. Use the fluid properties (for air and water) as listed in Table 1.1 and assume that the force F on the ball varies as F ∼ ρU2D2, where D is the ball diameter.
