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Expert: - 11/11/2008


Question
have a steel cylinder 5 ft long with a diameter of 4 ft.  -- 490 lbs per cubic ft. ....
calculate the weight ( load weight)
came up with wt=608.057 lbs....??  need to know how to solve
thanks

Answer
The way to solve it is to take the length (5 ft) times the area of the circle.  Note that the radius r is the diameter D over 2.

The area of a circle is πrē, so put r=d/2 in and the area A can be found.

The volume V is the area of the circle times the length times A.

Now that you have cubic feet (since all the measurements were in feet), you can take 490 * V and get the answer.

To summarize:

Take lenght L as 5, as given.
Take diamter d as 4, as given.
Take π as, you know, π.
Take radius r as d/2 = 2.
Take cross sectinal area A as πrē = 12.56637
Take volume V as LA = 62.831853
Take given density as Den = 490 lb/ft^3, as given.
Take weight as W as V*Den = 30,787.60801 .

Maybe it should actually be 30,788 or 31,000, depending on how accurate the initial measurements of 4ft and 5 ft were.

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