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August 21, 2014

Homework Help: Physics please check

Posted by Mary on Monday, April 9, 2007 at 10:12pm.

The "karat" is a dimensionless unit that is used to indicate the proportion of gold in a gold-containing alloy. An alloy that is one karat gold contains a weight of pure gold that is one part in twenty-four. What is the volume of gold in a 20.0 karat gold necklace whose weight is 1.09 N?


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Physics - DrRuss, Friday, April 6, 2007 at 1:24am
The sequence here is..

The implication in the question is to find out how much of the weight is gold, so do this using the fraction given.

Convert the weight to mass using F=ma and I would use a=9.8 m s^-2 unless your question/text book has a different value.

Now convert the mass to volume using density=mass/volume. The density of gold you will need to get from a data book, wikipedia, or maybe it is in the question/text book.



Please clarify this explanation.



For Further Reading


Physics, still don't get it! - DrRuss, Monday, April 9, 2007 at 1:07am
Could post what you have done so far?



Physics, still don't get it! - Mary, Monday, April 9, 2007 at 2:22am
F = ma

F/a = m

20.0/ 9.81 = 2.0387

density = mass/volume

volume = mass / 19300

volume = 0.0001056

This answer is incorrect. I am confused!



Physics, still don't get it! - bobpursley, Monday, April 9, 2007 at 6:24am
in your
mass=weight/g you put 20 for weight, That is not correct, it was given as about one newton.

Correct that, then 20/24 of that mass is gold.

Take the mass of gold, divide by the density of gold (look it up), and you have volume of gold.


IS MY WORKING OUT NOW CORRECT?



F = ma

F/a = m

(20.0/24.0 x 1.09N)/ 9.81 = 0.0926

density = mass/volume

volume = 0.0926/ 19300

volume = 0.000004798

You need to write the units as well as the numbers. 0.0926 kg is the mass of the gold

Divide that by the density for the volume. You did that. The answer you gave is in cubic meters. It equals 4.8 cubic centimeters

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