Have you seen the video of Harlem Globetrotter Buckets Blakes making the highest basketball goal off the top of the Tower of the Americas in San Antonio yet?
583 feet high!
The shot was made to commemorate World Trick Shot Day (yep, it’s real, 2nd Tuesday in December). Check it out!
— Harlem Globetrotters (@Globies) December 6, 2016
Do you see how the ball swooped out instead of going straight down?
Did you also see the backspin – the ball spinning back towards the tower?
Turns out these things are related – and make that basket possible.
The spinning motion causes something called the Magnus Effect. This is the same phenomenon that makes curve balls curve in baseball.
You can make your own flyer that takes advantage of this cool effect.
Here is what you need:
2 Styrofoam cups
Rubber band (longer is better but any will work)
Make your flyer
Put one cup on the table upside down and the other on top of the first right side up so that the bottoms of the cups are together. Wrap a piece of tape around the bottoms of the cups to hold them together. You can decorate the cups with markers if you like. The decorations make it easier to see the spinning motion.
Make the launcher
Cut a piece of string about 30 inches long. Tie one end of the string to the rubber band.
Launch your Magnus flyer
This is best done from a height – up the stairs, standing on a chair, over a balcony…
Wrap the string around the center of the flyer, where the cups are taped together. Stretch out the rubber band at the end of the string so that it goes once around the flier as well. Hold the flyer with one hand so that the rubber band comes out underneath the flyer. Stretch out the rubber band away from you and pull the flyer towards your face. Release the flyer. Watch it spin and glide!
So what is the Magnus Effect anyway?
When you release the launcher, the cups start to spin in the air. But if you look carefully the flyer is moving away from you but the cups are spinning towards you. This is called backspin. This backspin causes whirlpools of air behind the cups, which pushes the flier up and forward. In baseball the Magnus Effect is used to throw curve balls but instead of topspin the pitcher adds a sidespin, which causes the ball to turn (or curve) sideways.
Keep going! You can explore these questions for fun or even make this into a science fair project!
- What if you use smaller or larger styrofoam cups? What size cups gives the longest and highest flight?
- Does the length of the string in the launcher matter? Try using long rubber bands in a chain instead of the string. Which launcher gives the longest flight?
- What happens if you wrap the launcher around the flier in the other direction?