Visualizing Rotations: Understanding 3D Models Bounded by Parabolas

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Codyt
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Ok, I have to make a 3D model of a figure bounded by y=4 and y=x^2 that is rotated about the x-axis. I believe it will form an hour glass shape and I am putting two half spheres together to form the model, is this right?
 

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Codyt said:
Ok, I have to make a 3D model of a figure bounded by y=4 and y=x^2 that is rotated about the x-axis. I believe it will form an hour glass shape and I am putting two half spheres together to form the model, is this right?

No!...

(edit... if you revolve around the Y AXIS, THEN) It's called a "Paraboloid of revolution". It looks like a "Dot" (the candy made by the tootsie roll company)
 
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Can you please explain this, I looked up what you said, but I still cannot see how that would be formed by my shape. The paraboloid of revolution looks more like what would be formed by rotating in about the y axis. Anyh help is appreciated.
 
Codyt said:
Can you please explain this, I looked up what you said, but I still cannot see how that would be formed by my shape. The paraboloid of revolution looks more like what would be formed by rotating in about the y axis. Anyh help is appreciated.

You're right. I wasn't paying attention! I'll think about a good way to visualize this.