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Need help with physics question

  • Thread starter ramin86
  • Start date
  • #1
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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.
 

Answers and Replies

  • #2
jcsd
Science Advisor
Gold Member
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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
Tide
Science Advisor
Homework Helper
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Does this look familiar?

[tex]\frac {R_1}{R_2} = \left(\frac{M_1}{M_2}\right)^{\frac{1}{3}[/tex]
 
  • #4
42
0
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
42
0
Okay, nevermind, I got the answer at 9.469
 

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