A common problem in many introductory calculus courses is to calculate the amount of water that drains from a container, because it introduces accumulation of change over time.
And then it's in differential equations too since the rate is actually based on the pressure which is proportional to the height of the liquid in the tank
Because many calculus problems deal with rate of change as derivatives/integrals are important to solving them. A common word problem in calculus courses deals with tanks of fluid draining from a hole at the bottom as it deals with several factors that change over time.