### Hair Dryer Aerodynamics

```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?

```