SOLUTION: Pls help!!! : A coil of wire has a mass of 1.2 kg. The diameter of the wire is 2mm. 1cm^3 of the wire weighs 6.8g. Find the length of the wire and correct to the nearest metre.

Question 117415: Pls help!!! : A coil of wire has a mass of 1.2 kg. The diameter of the wire is 2mm. 1cm^3 of the wire weighs 6.8g. Find the length of the wire and correct to the nearest metre.
Found 2 solutions by edjones, josmiceli:
Answer by edjones(8007) (Show Source): You can put this solution on YOUR website!
x/1200=1/6.8 Proportion. Keep everything in g.
1200x/1200=1200/6.8
x=176.47cm^3
.
pi*r^2*L=volume
pi*(.2/2)^2*L=176.47 Keep everything in cm.
.1^2*pi*L=176.47
.01pi*L=176.47
.01pi*L/.01pi=176.47/.01pi
L=5,617.21 cm
=56 m
.
Ed

Answer by josmiceli(19441) (Show Source): You can put this solution on YOUR website!
The diameter of the wire is 2 mm
1 mm = .001 m
2 mm = .002 m
The cross-section area of the wire is

The volume of the wire is
where L is the length
Since a known volume has a known weight,
I can set up a proportion
6.8 g / 1 cm3 = 1200 g / V
1 cm3 = .0001 m3

multiply both sides by V

multiply both sides by 10^-4

divide both sides by 6.8

m
The length to the nearest meter is 5,617 m
check answer

close enough
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