Grades K–2 · Machines
How does wind make a pinwheel spin?
A pinwheel has blades arranged around a center. The center can turn on a small support. The blades are bent or tilted, so moving air meets them at an angle.
In the diagramShaped blades give air a turning effectmoving airThe shape and wind direction affect the turning motion.
The air pushes on the blades. Because those pushes act away from the center and have a turning effect, they can make the whole pinwheel spin. A flat sheet held in the wind would not necessarily turn in the same way.
Energy comes from the moving air. Friction at the center and other air forces resist the motion. When the breeze changes direction or becomes weaker, the pinwheel’s motion can change too.
About this explanation
Starting knowledge: Notice moving air and a wheel turning around its center.
Sources
- Science Buddies — Strong Wind Science: The Power of a Pinwheel