## anonymous 4 years ago The density of copper is 559 lb_m/ft^3. What is the mass of the copper pipe in pounds? A copper pipe, used for plumbing from the water main to a house, is 5 meters long and has a circular cross-section 3.2 cm in diameter. There is a 2.4 cm diameter hole in the center of the cross-section for the entire length of the rod.

1. Mertsj

I solved this for you yesterday. Why are you posting it again?

2. anonymous

it wasnt right

3. Mertsj

4. anonymous

you gave me 34.7, my software rejected it

5. Mertsj

And why do you have that underscore after the lb_ ?

6. anonymous

|dw:1328838221094:dw|

7. Mertsj

lb_m/ft^3 What does that mean?

8. anonymous

|dw:1328838314615:dw|

9. Mertsj

|dw:1328838358865:dw|

10. anonymous

pounds in mass

11. Mertsj

Is that different from pounds?

12. anonymous

yeah i think. im not quite sure what the conversion is but i think its different

13. Mertsj

14. anonymous

i think its something like 1lb_m = 2.2 kg/m^3

15. Mertsj

According to Wikipedia it's the same thing.

16. Mertsj

I'll work the problem again and see if I get a different answer.

17. anonymous

ok thank you

18. Mertsj

This time I got .983 pounds How many decimal places do you need?

19. Mertsj

How many times can you put it into your software? I am going to do it again to double check.

20. anonymous

unlimited

21. anonymous

until i get it right

22. Mertsj

I got the same thing again and I did it a different way. .983444164 lbs

23. Mertsj

Are you going to put it in and see if its right? I would like to know.

24. anonymous

i tried. it also rejected that answer

25. Mertsj

How many decimal places did you enter? Is there instructions for that?

26. anonymous

i entered all decimals

27. Mertsj

Maybe you should try 1 pound since they gave the density to the nearest pound. Or maybe try two significant digits since that's the number of significant digits in the diameter measurement.

28. Mertsj

Or maybe three significant digits since the density has 3 significant digits.

29. anonymous

yeah it rejected both again

30. anonymous

guess i will have to figure out something else

31. Mertsj

What class is this? maybe it's a calculus problem or something.

32. anonymous

its calc

33. Mertsj

Oh gees. The density is given per cubic foot. I have to recalculate.

34. anonymous

ok

35. anonymous

are you there?

36. Mertsj

yes

37. Mertsj

I found an online volume calculator for pipe. It allows me to put in the diameter in cm the length in m and get the volume in cubic feet. So I put them in, subtracted and got .06213 cubic feet and it came out to 34.73 lbs.

38. Mertsj

So maybe try 35 pounds or 34.73

39. Mertsj

Also I found online that the density of copper is 556 pounds per cubic ft. There isn't a typo in the problem is there?

40. anonymous

guess it wanted me to round the whole time, it took 35..wow

41. anonymous

can't believe it was that picky

42. Mertsj

Thank goodness. This was driving me crazy.

43. anonymous

thanks for the help very much

44. Mertsj

You're welcome. Good luck in all your studies.

45. anonymous

thank you. you too

46. Mertsj

ty

47. anonymous

take care

48. Mertsj

you too.