The simple models are all the same. Somehow, cram it in your head.

As long as we have only one component of acceleration, this is all we need to know. I'll ignore the units. You make sure everything works.

Ignore any vertical motion of the ball

an initial velocity of 100 ft/s

dv/dt = -1/10v

Now what?

Hint: The solution is NOT 2000 seconds. You tell me why.