Spinning Your Wheels: Pinwheel Sensitivity

Test Your Pinwheel

1. Prop up one of your pinwheels between two cushions or two stacks of books in a room that is free from drafts of air.
2. Extend and lock your measuring tape several feet on the floor from where the base of the pinwheel is located, straight back, as in Figure 2.
3. Label seven of the sticky notes from 0-6.
4. Look at the pinwheel. Count how many blades have been cut off. The first pinwheel you experiment with should have all eight blades, meaning zero have been cut off yet. Pick up the label that has the number of cut-off blades on it.
5. Turn the blow-dryer on low power, and hold it level with the pinwheel, as shown in Figure 2. Start right next to the pinwheel. Be sure the blow-dryer never touches the pinwheel to avoid burning. Slowly back up until the pinwheel stops turning. Turn off the blow-dryer and lower it straight down to the ground beside the measuring tape.
   
   
   Image Credit: Kristin Strong, Science Buddies / Science Buddies
   

   Figure 2. This shows how to set up the pinwheel and test it with a blow-dryer.
6. Mark the point at which the pinwheel stopped turning on the floor by placing the sticky note beside the measuring tape on the floor.
7. Look at the pinwheel and pick a blade to remove. Try to keep the pinwheel as symmetric as possible when you choose which blade to remove. Cut off the blade you have chosen with the scissors. The blade is attached to a front wheel and a back wheel, so you will need to make two cuts to remove it. Be careful with the scissors.
   
   Image Credit: Kristin Strong, Science Buddies / Science Buddies
   

   Figure 3. These photos show how to remove a blade from the pinwheel with two cuts.
8. Reposition your pinwheel between the cushions or stacks of books.
9. Repeat steps 4-8 until there is only one blade left. Be careful as you step backwards that you are not moving the sticky notes that are next to the measuring tape.

Record Your Measurements

1. Go to each of the labels on the floor and measure the distance at which it is located on the measuring tape. These are threshold distances. Record your measurements in your lab notebook in a data table.

   Data Table for Pinwheel Number 1
   Number of Pinwheel Blades Removed	Pinwheel Shape	Threshold Distance at Which the Pinwheel Stopped Turning (inches)
   0	Symmetric
   1	Asymmetric
   2	Symmetric
   3	Asymmetric
   4	Symmetric
   5	Asymmetric
   6	Symmetric

2. To ensure solid results, repeat steps 1-9 for the remaining two pinwheels, and record your measurements by making a new data table for each pinwheel. You should end up with three data tables.

Combine and Analyze Your Data Tables

1. Fill out the data table with the information from the other three data tables:

   Number of Pinwheel Blades Removed and Pinwheel Shape	Threshold Distance at Which Pinwheel Number 1 Stopped Turning (inches)	Threshold Distance at Which Pinwheel Number 2 Stopped Turning (inches)	Threshold Distance at Which Pinwheel Number 3 Stopped Turning (inches)	Sum of Threshold Distances (inches)	Average of Threshold Distances (inches)
   0 (symmetric)
   1 (asymmetric)
   2 (symmetric)
   3 (asymmetric)
   4 (symmetric)
   5 (asymmetric)
   6 (symmetric)

2. Plot the number of pinwheel blades removed (x-axis) vs. the average threshold distance in inches that it took for the pinwheels to stop turning (y-axis). You can make the line graph by hand or use a website like Create a Graph to make the graph on the computer and print it.
3. As more blades were cut off, what happened to the threshold distance? Was the threshold distance greater for symmetrical pinwheel shapes or asymmetrical pinwheel shapes?