- #1
shounakbhatta
- 288
- 1
Conservation of mass -- Stellar equation
Hello,
I was reading over a article on hydrostatic equilibrium of stars. I came across a chapter stating Conservation of Mass, where there is a sphere: r distance from the sphere, density as a function of radius ρ(r). Let m be the mass interior to r then the conservation of mass shows:
dm=4 pi r^2 ρdr.
Written in differential form:
dm/dr=4 pi r^2ρ
Now, I might be asking a silly question: I understand 4 pi r^2 is the surface area of a sphere. The law of conservation of mass states that mass of the system remains constant. Then how did the above equation arrives?
Can somebody please explain me, the equation how it arrives and its' connection to the law?
Thanks
Hello,
I was reading over a article on hydrostatic equilibrium of stars. I came across a chapter stating Conservation of Mass, where there is a sphere: r distance from the sphere, density as a function of radius ρ(r). Let m be the mass interior to r then the conservation of mass shows:
dm=4 pi r^2 ρdr.
Written in differential form:
dm/dr=4 pi r^2ρ
Now, I might be asking a silly question: I understand 4 pi r^2 is the surface area of a sphere. The law of conservation of mass states that mass of the system remains constant. Then how did the above equation arrives?
Can somebody please explain me, the equation how it arrives and its' connection to the law?
Thanks