When the dr/dt for sphere is constant and r=at + b, how does dV/dt change over time?
This is my work so far:
dr/dt = a
dV/dt = 4(pi)r^2 (dr/dt)
dV/dt = 4(pi)(at + b)^2 (a)
Well, if radius is steadily decreasing, is change in volume decreasing constantly.
I know in my work, since there is a variable t, volume would not change at a constant rate. But am I thinking about it correctly?
Let's assume that a and b are greater than zero. As you noted, dV/dt = 4a(pi)(at + b)^2. It's greater than zero anyway. So, V would increase while increasing t. Let's get d(dV/dt)/dt: d(dV/dt)/dt = 8(a^2)(pi)(at+b). It's also greater then zero, so, dV/dt would increase while increasing t, similarly.