iInertia Tutorial
Thank you for your interest in iInertia!
iInertia calculates the location of the centroid and the Moments of Inertia, Ix and Iy, about the centroid for a composite shape. Let's look at a classic example of a non-standard I-beam.
- Start up iInertia on your iPhone or iPod Touch.
- From the opening screen, tap on the "i" in the lower right hand corner.
- This is the list view. All the shapes that you add to build your
composite shape will be listed
here. The list view functions just like most of the other lists on an
iPhone/iPod Touch. You can scroll the list up and down and swipe a row
to
delete it as shown. Tap on the "+" sign in the upper right hand
corner to add a new shape.
- When you tap on the "+"
sign, you will see the dialog to add a
shape. You can add a rectangle, a circle, or a triangle, as either a
solid area or as a void, for example like a circular hole. We want to
add a rectangle and since this is the default shape to add, we can
start entering the data. If we had wanted to add a cricle or triangle,
we would tap the corresponding icon to change to that shape.
- To add the rectangle, we need to tell iInertia where the center
of the rectangle is and its height and width. As soon as you tap on one
of the text boxes, a keyboard appears. You do not have to hit return
after every entry, you can simple tap on the next text field and
continue. Tap return to have the keyboard move away. So adding a
typical rectangle would go like this; tap X and enter the x-location of the
center. Tap Y and enter the
y-location of the center. Tap "Height"
and enter the height of the rectangle. Tap "Width" and enter the width of the
rectangle. Tap "return" on the
keyboard to move the keyboard out of the way. After you have entered
all the dimensions, tap on "Add the
rectangle."
For this first rectangle, we need its center to be at (2.5, 0.0) and its height to be 1.0 and the width to be 5.0.
- iInertia will now be back at the list view. If we tap on the
"Done" in the upper left hand
corner, we can see what we have so far.
- iInertia is now back at the main screen with our one shape
displayed.
The location of the centroid is noted on the shape and also numerically
at the top of the display along with the moments of inertia about the
centroidal axis, Ix and Iy. We need to add two more rectangles, so we
tap on the "i"
at the lower
right to return to the list view and add them.
- Tap the "+" sign at the upper right of the list view and add a
second rectangle with its center at (2.5, 3.5) and a height of 5.0 and
a width of 1.0. When back at the list view, tap "Done". The main screen
should now look like this:
- Tap on the "i"
at the
lower
right of the main view to return to the list view and add our third and
final rectangle.
Tap the "+" sign at the upper
right of the list view and add a
third rectangle with its center at (2.5, 6.5) and a height of 1.0 and
a width of 5.0. When back at the list view, click done. The main screen
should now look like this, with our completed I-beam:
