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Standards of Length, Mass, and Time

  1. Jun 26, 2009 #1
    Two spheres are cut from a certain uniform rock. One has radius 4.30 cm. The mass of the other is two times greater. Find its radius.


    Not sure what equations to use for it

    I am not sure how to attempt this problem?
     
  2. jcsd
  3. Jun 26, 2009 #2

    Dick

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    Mass is volume times density. 'Uniform' rock means you can assume the two rocks have the same uniform density. Now do you know a relation between the radius of a sphere and the volume?
     
  4. Jun 26, 2009 #3
    Volume equals (4/3)pi radius^3
     
  5. Jun 26, 2009 #4

    Dick

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    Good then you are all set to go. Try solving it.
     
  6. Jun 26, 2009 #5
    Thanks I got it. So I set the two relations equal to each other m1/v1=m2/v2. Substitute volume for their equation of (4/3)pi radius^3 and solve for r2.
     
  7. Jun 26, 2009 #6
    The answer I got was 5.4 cm, which is right thanks again.
     
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