A 3 m dia weather balloon of spherical shape is to travel at 1.5 m/s. To determine the drag a model of dia 50 mm is to be tested in a water tunnel. Under dynamically similar conditions the drag on the...

A 3 m dia weather balloon of spherical shape is to travel at 1.5 m/s. To determine the drag a model of dia 50 mm is to be tested in a water tunnel. Under dynamically similar conditions the drag on the model was measured as 3.78 N. Calculate the test speed and estimate the drag on the balloon.