#### Modeling and Similitude: ConcepTest and Example Problem

Try to answer this ConcepTest and solve the example problem before using this module. Studies show that trying to answer the questions before studying material improves learning and retention. We suggest that you write down the reasons for your answers. By the end of this module, you should be able to answer these on your own. Answers will be given at the end of this module.

##### Example Problem 1

A newly-designed blimp will move at 15 mph through the air. To decide on what engines to use, you need to predict the drag force on the blimp. To do so, you place a 1:9 scale model in moving water in the laboratory.

a. Determine the water velocity needed to ensure similar flow characteristics.

b. The measured drag force on the model at this water flow rate is 700 lb. Estimate the drag on the prototype blimp and the power needed to move the blimp through the air.