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# Weight - Wrought Iron

Thu 19 Feb, 2015 05:24 pm
A wrought iron bar has the following dimensions:

1 square inch area of cross section.

1 yard in length.

Determine weight of bar.

Check my calculations:

Wrought iron weighs .28 lbs. per cu. inch.

Specific gravity of wrought iron - 7.78

1 x 1 x 36 = 36 cu. inches.

36 x .28 = 10.08 lbs.

1 x 1 x 36 = 36 cu. inches.

Weight of cu. in. of water - .2833 lbs.

Weight of cu. in. of wrought iron - .2833 x 7.78 = 2.204074 lbs.

Weight of bar - 36 x 2.204074 = 280.08 lbs.

Where did I make the error(s) ?

NON- Homework question.

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neologist

1
Fri 20 Feb, 2015 07:23 pm
@Randy Dandy,
I didn't look up your datum of .28 lbs.per cubic inch; but it sounds about right.
So, why did you think it necessary to go beyond 10.08 lbs.?

BTW, your figure for the weight of water seems excessive.
Try multiplying it by 1728 and see what you get.

Randy Dandy

1
Fri 20 Feb, 2015 08:28 pm
@neologist,
"So, why did you think it necessary to go beyond 10.08 lbs.?"
I wasn't .

A typo for the weight of water - 0.036127 lbs. per cu. in. - I had retyped the weight for the iron.

Weight of cu. in. of wrought iron - 0.036127 x 7.78 = 0.28106806 lbs.

Weight of bar - 36 x 0.28106806= 10.11804 = 10 lbs.

Correct ?

Randy Dandy

1
Fri 20 Feb, 2015 09:45 pm
@neologist,

Don't worry - I am not intelligent enough to do that. I have always struggled with math / algebra.
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neologist

1
Sat 21 Feb, 2015 11:16 am
@Randy Dandy,
Ok. I didn't see where or how you derived the weight/cubic inch of iron.
That's why I couldn't understand where figures re water came in
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