system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 What are the practical applications of calculus?

So this isn't a "learning calculus is pointless" post. I'm sure it's not pointless, but what is an example of how calculus is used to solve problems in the real world? I remember studying parabolas and such in high school but I didn't learn why, just memorized whatever I was supposed to. I took regular grade 12 math but didn't take calculus and have always been confused by what it actually is...
gpt
There are effectively no real-world engineering problems that don't involve calculus. Everything involving structures (houses, bridges, car bodies, boats), moving fluids (plumbing, sewers, airplanes, boats, car shapes), or control systems (thermostats, cruise control, power steering, autopilot, your oven) are resting on calculus because the governing equations are differential equations (a type of calculus-based equation).

Everything is subject to force = mass times acceleration, and acceleration is the second derivative (in the calculus sense) of position. So \*anything\* that involves solving for where or how fast or how hard something moves is calculus. Even the non-calculus-looking equations like "distance = 1/2 times acceleration times time squared", for distance under constant acceleration, is the solution to a specific differential equation. We just use it so often we often skip the calculus and go straight to the result.