This spinning helicopter is great fun!
NASA’s Ingenuity helicopter has made history by flying on Mars. To celebrate the first flight of a copter on another planet, here’s a simple unpowered helicopter you can build at home!
This spinning helicopter is great fun, but how does it work? There are two competing forces involved – gravity and air resistance.
When you let go of the copter, it’s pulled to the ground by gravity. However, the flaps at the top push lots of air out of the way on the way down. At the same time, the air is pushing against the flaps, slowing the copter’s fall.
This air resistance also has other effects. First, it bends the flaps back, making the whole copter more streamlined, and letting it fall faster. It also spins the copter, because the flaps are bent in different directions.
As the copter spins, the flaps are pulled outwards by the spinning. As they spread out, the copter starts falling more slowly, because the flaps are catching more air. Catching more air makes it spin faster too!
If you watch carefully, you can see this entire process unfold in just a second or two.
You might wonder what would happen if you dropped this spinning helicopter on Mars. The red planet only has one third the gravity of Earth, so the copter would fall slower at first. Then, Mars only has 1% of the density of Earth’s atmosphere. That means there wouldn’t be much air resistance slowing the copter or making it spin!
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