Hair Dryer Aerodynamics Tiger Den 2 Project - Build a Hovercraft Hovercraft float on a cushion of air Real hovercraft can cross both land and water How a Hovercraft Works Fan makes an “air cushion” – Air cushion holds up hovercraft – Air cushion means less “friction” Some Tiger Tests Can the hairdryer move the hovercraft without the air cushion? Does the hovercraft work on the rug? How much can the hovercraft carry? How can I steer the hovercraft? What happens when a corner goes off the table? ... Experiment: Wind Tunnel Test Track Bill’s Hypothesis (Guess): – Wind will slow down the cars with the biggest sails The Experiment – Tigers race cars down track into wind – Tigers see if cars with biggest or smallest sails win Controls for Experimental Error (How do we fix known problems with the test) Are some cars just slower than others? – Tigers race cars with fan off and fan on – Tigers race every car against every other car Are the tracks fair? – Tigers run each race twice – switching tracks Test Results Comparison with Hypothesis Some Questions What would happen if the wind blew down from the top? – Try it! Did Bill prove his hypothesis? Are there other things wrong with the test? What happens if the track is at a different height?