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Consider an expanding sphere of instantaneous radius R whose total mass remains constant. The expansion is such that the instantaneous density ρ remains uniform throughout the volume. The rate of fractional change in density ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ ρ dt dp 1 is constant. The velocity v of any point on the surface of the expanding sphere is proportional to
- R 3
- R
- R 1
- R 2/3
Correct answer: R
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