Case fan issues

[barkloaf]

Today, I turned on my computer, and was greeted a weird fan noise. I moved my tower to a better place for diagnosis, and found the fan that was making the noise. I unplugged that fan, turned the computer back on. Then this happened:

 

It still spun, despite being unplugged, but didn't make the weird noise.

 

What is going on here?

I haven't plugged the fan back in yet.

[satiresite]

I think something got inside the fan, can you open it?  

[barkloaf]

2 minutes ago, satiresite said:

I think something got inside the fan, can you open it?  

My real question is more

 

Why is the fan spinning when not plugged in?

[satiresite]

Because it still has momentum. 

[barkloaf]

2 minutes ago, satiresite said:

Because it still has momentum. 

But It stopped before I unplugged it...

[satiresite]

Open it up, that's the only way to find out for sure. 

[stefanDB]

its magic! 

probably because other fans are causing air to flow through it and make it spin, or something magnetic is turning it, but that seems unlikely