What is the weight of four round iron plates that are each 5" in diameter and 1/4" thick, given iron weighs 490 lbs/ft³?

To find the weight of the four round iron plates, first calculate the volume of one plate and then multiply it by the density of iron to determine the total weight.

Each plate is a cylinder, and the volume ( V ) of a cylinder can be calculated using the formula:

[ V = \pi r^2 h ]

where ( r ) is the radius and ( h ) is the height (or thickness in this case).

Given the diameter of each plate is 5 inches, the radius ( r ) is:

[ r = \frac{diameter}{2} = \frac{5, \text{in}}{2} = 2.5, \text{in} ]

The thickness ( h ) is 1/4 inch. Now, we can express the volume for one plate in cubic inches:

[ V = \pi (2.5, \text{in})^2 (0.25, \text{in}) = \pi (6.25, \text{in}^2) (0.25, \text{in}) = \pi (1.5625, \text{in}^3) \