Nature's Airfoils 

Eileen Wild                    Retired
                           

Objective:

To show that objects affected by air resistance have a slower rate of fall.  
This topic is suitable for the middle and upper grades.

Equipment:

Winged seeds (Maple, Ash, Linden), rocks, feathers, toy balloons (optional)

Background:

The correct name for winged seeds of the Maple, Ash and other trees is Samara.  
They are considered to be flat wings with their mass distributed along the "x" 
axis from the seed to the wing tip.  Samara means flat wing.  The wings on the 
seeds act as airfoils by deflecting the airstream downwards.  This downward 
motion results in a reaction force upwards known as a lifting force. You have 
learned that in a vacuum all objects fall at the same rate regardless of their 
mass.  Today you will discover the effect of air resistance on seeds by timing 
their descent and measuring the distance they have fallen. 

Strategy:

The two stairwells from the third floor to the ground level will be the location 
for this experiment.  The following is the order in which you will conduct it. 
1.  Drop the rock and time its descent. 
2.  When you drop the single and double winged Samaras use different  
    orientations of the seed pod.
3.  The feather is the last object to be dropped.
4.  Measure the distance from the top floor to the ground level.

Conclusions:
                   Seed Up       Seed Down      # Rotations  Time
______________________________________________________________________
| Rock            |            |                |          |         |
|_________________|____________|________________|__________|_________|
______________________________________________________________________
| Single Wing     |            |                |          |         |
|_________________|____________|________________|__________|_________|
______________________________________________________________________
| Double Wing     |            |                |          |         |
|_________________|____________|________________|__________|_________|
______________________________________________________________________
| Feather         |            |                |          |         |
|_________________|____________|________________|__________|_________|