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Finding Mass of a Sphere

  • Thread starter Ripcurl
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  • #1
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Homework Statement


A sphere of metal has a radius of 5.3 cm and a density of 8.15 g/cm3. What is the mass of the sphere? Answer in units of g.


Homework Equations


Density=mass/volume

Volume of a sphere=4/3лr^3


The Attempt at a Solution


I found the volume by multiplying 4/3 by л and 5.3 squared. I got 66.1850323. I plugged this into the formula for density, manipulated it to get mass by itself and got 539.4118513. This answer seems really unreasonable. I think I need to do some conversions but I'm not sure what to convert. I think I need to convert the radius to meters but the density is in grams/cm cubed and I need to answer in units of grams.
 
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Answers and Replies

  • #2
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Mass = density times volume

First, volume of a sphere is 4/3[itex]\pi[/itex]r^3.

Next, don't convert anything you've been given the right units for what you've been asked for. Produce a volume for the sphere in terms of cm^3, then

[itex]cm^3[/itex] * [itex]\frac{g.}{cm^3}[/itex] = [itex]g.[/itex]
 
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  • #3
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So you're saying find the volume. I got 623.6145193 cm^3. Then I multiply that by the density (8.15) to get the mass. I get 5082.458333. That doesn't seem right. XD
 
  • #4
19
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But it is. Wow. You're amazing! Thanks! XD
 
  • #5
45
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Glad to help.

Remember that the equation of finding the mass of a sphere is

Mass = density times volume
 
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