7. Second Moment of Area (Moment of Inertia)

Try these first

1. 1.

   What is the formula for the moment of inertia of a rectangle?

   Hint

   Think about the base and height of the rectangle.

2. 2.

   Calculate the moment of inertia for a rectangular beam with dimensions 4 in (base) and 6 in (height).

   Hint

   Use the standard formula.

3. 3.

   What is the Moment of Inertia for a circle with a diameter of 4 in?

   • (π/32) * 4^4
   • (π/64) * 4^4
   • (π/2) * 4^4

   Hint

   Recall the standard formula for circles.

4. 4.

   True or False: A larger Moment of Inertia indicates a beam is less resistant to bending.

   • True
   • False

   Hint

   Think about what I represents.

5. 5.

   A beam has a rectangular cross-section of 10 cm wide and 20 cm high. Calculate its Moment of Inertia about the neutral axis.

   Hint

   Use the rectangle moment of inertia formula.

6. 6.

   Determine the Moment of Inertia for a composite I-section beam where the flange is 5 cm wide and 2 cm thick and the web is 8 cm high and 1 cm thick. Calculate separately, then sum.

   Hint

   Break down into flange and web, apply the rectangle formula.