How Do You Determine the Radius of a Sphere If Its Mass is Seven Times Another?

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In summary, the conversation discusses finding the radius of a sphere with a certain mass and the average density of an object. The formulas for average density and volume of a sphere are provided and the conversation ends with the solution of 9.46984375 cm for the radius.
  • #1
ramin86
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I'm really bad at physics and need help with the following question:

Two spheres are cut from a certain uniform rock. One has radius 4.95 cm. The mass of the other is seven times greater. Find its radius.
 
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  • #2
The average density of an object is:

[tex]\rho = \frac{m}{V}[/tex]

Where m is mass and V is volume

The volume of a sphere is:

[tex]V = \frac{4\pi}{3} r^3[/tex]

Where r is the radius.

These are the only two formulas you need.
 
  • #3
Does this look familiar?

[tex]\frac {R_1}{R_2} = \left(\frac{M_1}{M_2}\right)^{\frac{1}{3}[/tex]
 
  • #4
Alright, well I got a volume of 508.05 for the sphere with a radius of 4.95, but still not exactly sure of where to go from here.
 
  • #5
Okay, nevermind, I got the answer at 9.469
 

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