Chemistry converting

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andrea

2009-06-24 2:47 pm

1)

A copper wire (density = 8.96 g/cm3) has a diameter of 0.49 mm. If a sample of this copper wire has a mass of 33 g, how long is the wire?

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2)

A star is estimated to have a mass of 1 1036 kg. Assuming it to be a sphere of average radius 6.5 105 km, calculate the average density of the star in units of grams per cubic centimeter.

更新1:

im sorry but you are wrong.. i cant get it right in my assignment.

回答 (1)

Prof. Physics

2009-06-24 4:03 pm

✔ 最佳答案

1. Diameter, d = 0.49 mm = 0.049 cm

Surface area, A = pi(d/2)2 = pi(0.049/2)2 = 1.886 X 10-3 cm2

Let L be the length of the wire,

Volume of the wire, V = AL

And Volume X density = Mass

So, pAL = m

(8.96)(1.886 X 10-3)L = 33

Length, L = 1953 cm = 19.5 m

2. Volume of the star, V

= 4/3 pir3

= 4/3 pi(6.5 X 1010)3

= 1.15 X 1033 cm3

Since Volume X density = Mass

p(1.15 X 1033) = 1 X 1039

Density, p = 8.69 X 105 gcm3

參考: Physics king

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