![Spacer](../../../../img/new_iface/main_iface/pix_dkblue.gif) |
![Tab](../../../../img/new_iface/aero/tab.gif) ![Homepage Button](../../../../img/new_iface/aero/sidebar_links/1.gif) ![What is NASA Quest Button](../../../../img/new_iface/aero/sidebar_links/2.gif) ![Spacer](../../../../img/new_iface/aero/sidebar_links/dotted_sidebar.gif) ![Calendar of Events Button](../../../../img/new_iface/aero/sidebar_links/3.gif) ![What is an Event Button](../../../../img/new_iface/aero/sidebar_links/4.gif) ![How do I Participate Button](../../../../img/new_iface/aero/sidebar_links/5.gif) ![Spacer](../../../../img/new_iface/aero/sidebar_links/dotted_sidebar.gif) ![Bios and Journals Button](../../../../img/new_iface/aero/sidebar_links/6.gif) ![Spacer](../../../../img/new_iface/aero/sidebar_links/dotted_sidebar.gif) ![Pics, Flicks and Facts Button](../../../../img/new_iface/aero/sidebar_links/7.gif) ![Archived Events Button](../../../../img/new_iface/aero/sidebar_links/8.gif) ![Q and A Button](../../../../img/new_iface/aero/sidebar_links/9.gif) ![News Button](../../../../img/new_iface/aero/sidebar_links/10.gif) ![Spacer](../../../../img/new_iface/aero/sidebar_links/dotted_sidebar.gif) ![Educators and Parents Button](../../../../img/new_iface/aero/sidebar_links/11.gif) ![Spacer](../../../../img/new_iface/aero/sidebar_links/bot_spacer.gif)
![Highlight Graphic](../../../../img/new_iface/aero/highlight.gif)
![Sitemap Button](../../../../img/new_iface/aero/sitemap.gif) ![Search Button](../../../../img/new_iface/aero/search.gif)
|
|
This experiment is designed to teach your students about
the properties of lift. For a printable version with data tables click
here.
![Introduction](titles/intro.jpg)
An airplane has four primary forces acting on it: lift,
drag, weight, and thrust. In this experiment, the lift is being examined.
The lift of the airplane is the aerodynamic force that elevates it into
the air and holds it there. For an explanation on how wings create lift,
see Forces on an Aircraft.
The purpose of this experiment is to discover the properties
of lift.
![Materials](titles/materials.jpg)
- bicycle pedals 1/2" thread
- 1/2" brass (water piping) tee
- 3/8" diameter wooden dowel
- 3"x36"x1/16" balsa wood
- clamp
- fan
- manila folder
- paper tubes
- glue
- razor blade
- binder clip
- paper clips
- Ping-Pong ball
- string
- protractor
Alternatives:
- other type of bearing for bicycle pedal
- text books or other weight for clamp
- quart-sized milk cartons for paper tubes
- modeling clay for binder clip and paper clips
- pitot tube for Ping-Pong ball, string and protractor
![Procedure](titles/procedure.jpg)
I. Set up the Wings (estimated time: 15 min.)
- Cut the 3/8" diameter dowel to 26" inches
- Cut out different sized wings of similar shape
from 1/16" balsa wood using a razor blade (we chose four sizes of 30°,
60°, 90° triangles)
- Cut a manila folder into a rectangle 8" x the
length of your wing. Cut as many rectangles as you have sets of wings
- Roll each piece of folder into a cylinder that
fits snugly around the dowel
- Glue each group of similar sized wings spaced evenly
onto their respective cylinders
- click here for pictures
II. The Flow Straightener (estimated time: 30 min.)
- Roll pieces of 8"x11" paper into cylinder with
a 1" or 2" diameter and 11" high
- Glue all the cylinders together to cover the front
of your fan
- Another way to make a flow straightener is to
glue together cut-open milk cartons
III. Setup (estimated time: 10 min.)
- Slide the dowel through the brass T, so the T
is roughly in the middle of the dowel
- Use tape or rubberbands to secure the dowel in
place
- Screw the brass T with the dowel onto the bike
pedal
- Clamp bike pedal onto a table so the dowel swings
freely
- Place the fan in front of the dowel making sure
that you don't obstruct the swing of the dowel
- Clip a binder clip onto the front end of the dowel
- Mark an angle for your dowel to fly at. A good
angle would be anywhere less than 15 degrees from horizontal
- click here for more pictures
IV. Run the Experiment (estimated time: 20 min.)
- Use a method to measure the speed of the wind
at each fan speed (click here
to find out how we did it with a Ping-Pong ball)
- Place the largest tail onto the end of the dowel
- Hang enough paper clips onto the binder clip so
that the dowel is balanced
- Take off all the paper clips
- Turn fan on highest setting
- Start hanging paper clips off of the binder clip
until the dowel flies at your specified angle
- Record how many paper clips you used
- Lower fan speed and repeat step 6 until you are
out of fan speeds
- Change the size of the tail pieces and repeat steps
3 through 7 until you have used all of your wings
- click here for video clips
V. Analyzing the Data (estimated time: 20 min.)
- Calculate the force of lift by setting the sum
of every torque to zero (use our formula)
- Plot the lift for each wind speed against the wing
sizes
- Plot the lift for each wing size against the wind
speed
![chart of weight](data_pics/chart.jpg)
Using this data, the lift force can be calculated using
the equation .
To see how this is derived and to see our calculations, click
here.
![chart of wind speed and lift](data_pics/chart3.jpg)
![chart of wing size and lift](data_pics/chart2.jpg)
![graph of wind speed vs lift](data_pics/windspeed1.jpg) ![graph of wind speed squared vs lift](data_pics/windspeed.jpg) ![graph of wing size vs lift](data_pics/wingsizel.jpg)
![Analysis](titles/data1.jpg)
- What do you notice about the relationship between
the lift force and the wing size?
- What do you notice about the relationship between
the lift force and the wind speed?
- Which wind speed and which wing size produced
the most accurate results? The least accurate? Why do you think this
is?
- What could have affected your results
- How could you improve the experiment (setup, materials,
data collection)?
- The relationship between the lift force and the
wing size is directly proportional
- The lift force is proportional to the wind speed
squared
- Wing size #3 and the medium wind speed produced
the most accurate results. The largest wing size and the fastest wind
speed produced the least accurate results. There are many factors affecting
the accuracy of the measurements that have the least effect at the medium
fan speed and wing size #3. The first is the stickiness in the bearing.
The more lift the wing produces the less the effect of the bearing's
resistance and the granularity of the increment of measure (paper clips)
can affect the results. This implies that the most accurate measurements
should take place at the highest wind speed and largest wing size, and
the least accurate should be slowest wind speed and smallest wing size.
However, another factor, disparities in the wind flow and wind speed,
increases at larger sizes and speeds. A larger wing covers more area,
and since more variation in the airflow can occur in a larger area,
the largest wing might not yield the most accurate results. At the highest
wind speed, the wings all experienced increased movement, which hindered
taking the data. All of these factors led to the medium wind speed and
wing size's greater accuracy.
- The stickiness in the bearing affected the results
because it provided a force that resisted the direction of motion. If
this force was greater than the torque on the dowel, the dowel would
stop. This translates into less accurate balancing for the different
wing sizes. Variations in the air speed and turbulence in the air, even
after the flow straightener, could have affected the lift. This error
might have increased the force for some wings and decreased it for others
- The experiment could be improved by 1) finding
a smoother bearing, to decrease turning resistance 2) measuring the
wings' performance at at least 15 different windspeeds (5 different
distances from the fan), to get clearer results, 3) trying the experiment
at different angles of attack below 10 degrees to further test the results'
relationships.
![Conclusion](titles/conclusion.jpg)
The data shows that the lift force and the square
of the wind speed are directly proportional. The lift force and the size
of the wing are also directly proportional. The data is not completely
linear due to sources of error, which include: inconsistent wind speed,
sticky ball bearings and slight swirl from the fan blades.
|
|