A cubic foot of distilled water at the maximum density, at the level of the sea, and the barometer at 30 inches, weighs 621⁄2 pounds or 1000 ounces avoirdupois.
By actual measurements, it has been found that a bushel, dry measure, contains about 11⁄4 cubic feet. This makes it easy to estimate about how many bushels any bin will hold.
Practical Applications of Cubic Measure
Example: An open tank made of iron 1⁄4 inch thick, is 4 feet long, 2 feet 6 inches broad, and 2 feet deep, outside measurement. Assuming that iron weighs 7.8 times as much as water, find the weight of the tank.
The external volume of the tank = 2 × 21⁄2 × 4 cubic feet = 20 cubic feet.
Since the iron is 1⁄4 inch thick, the inside length is 1⁄2 inch less than the outside, the inside breadth is 1⁄2 inch less than the outside, and the inside depth is 1⁄4 inch less than the outside.
Therefore the interior volume
= 291⁄2 × 471⁄2 × 233⁄4 cubic inches
= 59 × 95 × 9516 cubic inches
= 3327911⁄16 cubic inches