[nikita]

i dont even know what theyre asking for here, but i think if someone could tell me, i can solve it.

a roll of aluminum wire is used to make finishing nails.  if the nails are 5.00 cm long and .300 cm in diameter and the roll has a mass of 225 kg, how many nails can be made from one roll?

now im thinking of a nail with no head and i picture a cylinder.  apparently, i am to use the formula for the volume of a circle with length (eg. pi * r^2 * l).  does anyone know why?  a nail with no head is not a circle to me.  anyway, i get this far, using the formula for a circle with length:

pi*r^2 * l = 3.14*.0225*5= .353cm
so i guess the volume is .353cm

so, then what?  i need to find out a number rather than a weight

maybe if i knew why i was using the above formula, i wouldnt be so mystified. 

[nj_bartel]

i dont even know what theyre asking for here, but i think if someone could tell me, i can solve it.

a roll of aluminum wire is used to make finishing nails.  if the nails are 5.00 cm long and .300 cm in diameter and the roll has a mass of 225 kg, how many nails can be made from one roll?

now im thinking of a nail with no head and i picture a cylinder.  apparently, i am to use the formula for the volume of a circle with length (eg. pi * r^2 * l).  does anyone know why?  a nail with no head is not a circle to me.  anyway, i get this far, using the formula for a circle with length:

pi*r^2 * l = 3.14*.0225*5= .353cm
so i guess the volume is .353cm

so, then what?  i need to find out a number rather than a weight

maybe if i knew why i was using the above formula, i wouldnt be so mystified. 

Don't overcomplicate it.  Ignore the nail premise.  Read the question as 'You're making Al cylinders with a 5 cm length and a .3 cm diameter.  You have 225 kg of Al stock to make these cylinders.  How many cylinders can you make?'  Try to answer it from there.

[nikita]

ok, completely ignore my rantings about the formula for a cylinder.  i am henceforth ignoring the back cover of my book which has led me astray.

i tend to overanalyze everything.  sometimes this is good, but not today.

well, im officially an idiot because i have no idea how to apply mass and volume to a number of nails.  i guess i have the volume of each separate nail, and now i need to find the mass of each nail?  i know the total mass.  then maybe each nails mass with the total mass, somehow will give me the number of nails?

[nj_bartel]

Are you given the density of Al in your book anywhere?

 http://wiki.answers.com/Q/What_is_the_density_of_aluminum

[nikita]

duh.  this is how you can tell i havent taken chem in 10 years.  i get it now.

m= dv
m= 2.7*.353
m = .953g

mass for each nail is .953g and total mass is 225kg

22500g/.935g = 2.25x10^5 nails.

thank you.  i think i know what im missing in these probs now. 

[nj_bartel]

didn't check your math, but looks good

[nikita]

thanks.

the math was wrong because i transposed some numbers, but the solution is

m = dv
m= (2.698)(.353)
m= .952

m=225kg = 225000g
225000g/.952g =  2.36 x 10^5 nails.