Do fins help an object rotate? example, a nerf football
It depends on their orientation. Fins are usually used to help stabilize an object, i.e rocket or missile. If the fins are not parallel with the flow around it then they will impart a spin most likely.
Do you have a specific situation in mind that you are wondering about?
i made this cylinder, and put four fins on the top of it, and it is supposed to go straight down, but one of my fins is bent a bit, and it causes the vehicle to spin as it falls down, and i was curious on why it does that
I assume the shark's fin prevents from making a stupid rotation when rushing for its prey..
More info on this?
The bent fin causes the rotation because it induces aerodynamic rolling forces on the cylinder body. In fact, any surface which intrudes into the airstream is pushed by that airstream, hence pushing the cylinder body. If these pushing forces are not anti-symmetric or coupled in such a way as to cancel each other out, then you are bound to see some kind of unexpected motion of the cylinder body, such as a roll or a shimmy.
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