There's a problem I can't figure out in my homework. I can't really understand what it's asking. Maybe someone can help.
A meteor enters the Earth's atmosphere and burns up at a rate that, at each instant, is proportional to its surface area. Assuming that the meteor is always spherical, show that the radius decreases at a constant rate.
I think the problem is asking me either to show that $\frac{dr}{dt} = 0$ (which I don't know how to do) or that the relationship $\frac{dV}{dt} / \frac{dA}{dt}$ has no parameter $\frac{dr}{dt}$, which I've done, I think.. $\frac{dV}{dt} / \frac{dA}{dt} = \frac {r}{2}$