Expert: Steve Holleran - 9/9/2007

Question
Hi Stave!
I have been asked the following question: A cylinder is made of solid aluminum that has a unit weight of 165 pounds per cubic foot. What is the weight of this cylinder. Round up your answer to the nearest pound.

Remember that V = 3.14 x Radius squared x Height. The weight per square foot per inch of thickness of aluminum is 14.5.

The diameter of the cylinder is 6 ft. and the height is 5 ft.

I have come up with several answers (4637, 3886 and a few others, that were incorrect).

Can you solve this problem and explain to me how you came about your answer? Thanks!

Alice


Answer
Hi Alice,

Well, you've got the correct formula to use here.  I'm not sure what the 14.5 has to do with anything.  I would work it this way:

        V = 3.14 * 3^2 * 5 = 141.3 cubic ft.

(Remember, the diameter is 6, so the radius is 3)

Then since aluminum weighs 165 lb/ cu. ft, just multiply:

        Weight = 141.3 cu. ft * 165 lb/ cu. ft.
             
               = 23,314.5 lb

I hope this is what you need.

Steve Holleran