Science Buddies: "Ask an Expert"

My son is doing a version of the Make the Wind Work for You Experiment listed on Science Buddies. He is doing the variation where he changes the size of the rotor blades. We are having trouble with coming up with the correct procedure. He is testing what wind blade design (size of the blades) produces the most energy. Does he need to add washers for the weight as the directions say on the website, or should he do something different? Also, should we use an anemometer to measure the wind speed?

Hi!

This experiment looks really cool!

Firstly, the washers are only a stand-in for a weight. I would assume the experiment writer chose them because they are fairly common and lightweight. So, if you don't have any washers, you can tie a different weight to the string in order to find out which rotor design is the best. For example, you could use nuts or bolts instead. As long as you can tie the weight to the string and it is light enough to be an accurate measurement of the rotor's power, you should be able to use it. Also, it could be helpful to weigh each weight that you choose to use (with a gram scale), so that you can be more accurate with your data collection.

Secondly, you shouldn't need to use an anemometer, as the fan (which creates the wind) can be set to a constant setting for all of the rotor types. The important part of the experiment is not the exact wind speed, but the effectiveness of the rotor blades. Therefore, as long as the wind speed is kept the same, then you should be able to tell which rotor blade is the best.

Hope this helps!