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## What is cross sectional area of a wire?

Most wire is made with a circular cross section of some particular radius and diameter. Then we define the cross sectional area simply as the square of the wire’s diameter in mils and call that our area in units of “circular mils.” This makes number handling ever so much easier.

## How do you calculate the volume of a shell?

The volume of the cylindrical shell is then V = 2πrh∆r. Here the factor 2πr is the average circumference of the cylindrical shell, the factor h is its height, and the factor ∆r is its the thickness.

## What is the shell radius?

The radius of each cylindrical shell is the horizontal distance from the current x value to the axis of rotation. So if we rotate about the line x=2, the distance between our current x position and the axis of rotation is 2-x. Likewise, if we rotate about the y axis (aka x=0) the radius is x-0=x.

## How do you determine shell height?

Draw a thin horizontal strip of width “dy” at height y, and imagine rotating it about the x-axis. The strip is at height about y, so it sweeps out a thin cylindrical shell, of radius y. The “height” of the shell is the length of the strip. It is just x.

## How do you do the cylindrical shell method?

Use the shell method to compute the volume of the solid traced out by rotating the region bounded by the x-axis, the curve y = x3 and the line x = 2 about the y-axis. Here y = x3 and the limits are from x = 0 to x = 2. is rotated about the y-axis, find the volume of the region traced out.

## How do you know when to use cylindrical shell method?

The Cylindrical Shell method is only for solids of revolution. Used when it’s difficult to to use the Washers/Slices (Sect 5.2) method because it’s messy to draw our rectangles perpendicular to the axis of revolution.

## Is the shell method the same as the washer method?

The main difference between the washer and shell methods in calculus is the orientation to the axis of rotation. The washer method you use a dx if you rotate around the x axis. The shell method, you use dy for rotation around the x axis. The washer method is used between two curves.

## What is H in the shell method?

Key Idea 25: Shell Method. Let a solid be formed by revolving a region R, bounded by x=a and x=b, around a vertical axis. Let r(x) represent the distance from the axis of rotation to x (i.e., the radius of a sample shell) and let h(x) represent the height of the solid at x (i.e., the height of the shell).

## What is the shape of a spherical shell?

In geometry, a spherical shell is a generalization of an annulus to three dimensions. It is the region of a ball between two concentric spheres of differing radii.

## How do you use the washer method?

1. Determine where the two curves intersect. So the solid in question spans the interval on the x-axis from 0 to 1.
2. Figure the area of a cross-sectional washer.
3. Multiply this area by the thickness, dx, to get the volume of a representative washer.
4. Add up the volumes of the washers from 0 to 1 by integrating.

## How do you integrate with shells?

These are the steps:

1. sketch the volume and how a typical shell fits inside it.
2. integrate 2π times the shell’s radius times the shell’s height,
3. put in the values for b and a, subtract, and you are done.

## When would you use the shell method instead of disks washers?

So if I have to find the volume of the solid generated by revolving the region bounded by x=0 , y=x2 , and y=−x+2 around the y -axis, I would use shells because there would only be one integral to evaluate. (Disks would require two: one from y=0 to y=1 and another from y=1 to y=2 .)

## Can Volume negative?

Yes, volumes can be 0, but volumes can never be negative. The volume of a square is 0, for instance. You might want to look into measure theory and lebesgue measures.

## How do you solve for negative volume?

Some approaches that can help to overcome negative volumes include the following:

1. Simply stiffen up the material stress-strain curve at large strains.
2. Sometimes tailoring the initial mesh to accomodate a particular deformation field will prevent formation of negative volumes.
3. Reduce the timestep scale factor.

## How do you use a negative volume index?

The Negative Volume Index (NVI) is a cumulative indicator, developed by Paul Dysart in the 1930s, that uses the change in volume to decide when the smart money is active. The NVI assumes that smart money will produce moves in price that require less volume than the rest of the investment crowd.

## Can the volume of a parallelepiped be negative?

The scalar triple product can be positive, negative, or zero. (That’s why we need the absolute value for the volume.)

2020-08-16