Weight, Length

[Guest]

I have two problems:

1) A length of copper wire has the following dimensions:

Thickness - 1/8 inch.

Length - 20 yards.

Specific gravity of copper - 8.8

Cubic foot of water - 62.5 lbs. = 1000 oz.

Determine weight of wire.

My partial calculation:

1/8 inch = .125 = .01041 feet

20 yards = 60 feet

.01041 x 60 = .6246

I am not sure from here.


2) A copper wire has the following description:

Thickness - .2 cm

Weight - 1 kg

Determine length of wire.

I am not sure how to solve.

[Guest]

Please respond to my questions. Thanks.

[Guest]

Cubic foot of water - 62.5 lbs. = 1000 oz.
Cubic foot of copper = 1000 x 8.8 = 8800oz.

1/8 inch = .125 = .01041 feet

20 yards = 60 feet

(0.01041 x 0.01041 x 3.142/4) x 60 = 0.005107 cu. feet copper

0.005107 x 8800 = 44.945 oz. copper = 2.81 pounds

.........................Simple...........................

[Guest]

"0.01041 x 0.01041 x 3.142/4) x 60 = 0.005107 cu. feet copper"

I have two questions:

Is the wire considered a thin cylinder ?

How do I set up problem 2) to solve ?

[Guest]

in these questions we are taking the cross section area to be a circle. (solid circle)

sometime a thin cylinder is a hollow cylinder having a thin wall as in a copper pipe
and a thick cylinder is still a pipe but with a thicker wall.


Thickness - .2 cm ....the diameter of the circular cross section, you will need to calc. the area

Weight - 1 kg ....weight of the copper

Determine length of wire.

You will have to use the density to convert the 1 kg weight into cu feet

Then divide the cu. feet by the cross section area to get the length

[Guest]

Sorry I see the units are mixed cms, kg, cu feet, in, lbs etc
You will also have to convert to keep all units compatable.

[Guest]

"Thickness - .2 cm ....the diameter of the circular cross section, you will need to calc. the area

Weight - 1 kg ....weight of the copper

Determine length of wire.

You will have to use the density to convert the 1 kg weight into cu feet

Then divide the cu. feet by the cross section area to get the length"


Check my calculations:

Volume - 3.14 x .1 cm x .1 cm = 3.14 cm.^2

1 kg - 1000 grams.

3.14 x .1 x .1 x 8.8 = .276 (not sure what this is called).

1000 /.276 = 3,623.18841 cm. /100 (cm in meter) = 36.23 meters.

Not sure.

[Guest]

you have got the correct answer but I think there are mistakes in some of the stages of your working out.
You can compare with mine

Area of section of the wire = 3.14 x 0.1 x 0.1 = 3.14 x 0.01 = 0.0314 cm^2

There is 1000 g of copper wire.
density of water = 1 g per cc or 1 gram per cm^3

density of copper is 8.8 x 1 gram per cm^3 OR 1 cm^3 of copper is 8.8 grams

So volume of copper is (1000 / 8. cm^3

Length = volume divided by area

= (1000 / 8. / 0.0314 = 3619 cms = 36.19 metres.

...............................Simple...................................

[Guest]

Thanks. Can you provide some tips on converting units ? I always have difficulty and get confused.

[Guest]

Converting units is just a form of dimensional analysis
OR the algebra of dimensional analysis
(miles per hour)x(hours per day) = (m/h)x(h/d)
the "h"s cancel and left with m/d OR miles per day

to multiply by h/d same as divide by (d/h)

so m/d divided h/d is same as m/d x d/h
the "d"s cancel and left with m/h

[Guest]

Thanks.