Stationary-action principle
The stationary-action principle is a very smart idea that helps scientists and engineers understand how things move and change over time, like when a ball is thrown, a car is driving or a rocket is flying.
To make it easy to understand, let's imagine you are playing a very fun game called "Follow the Leader". The leader (let's call him or her Steve) will lead you and your friends across a playground. Steve can walk, run, or even jump to get across.
Now, let's say that Steve wants to lead everyone across the playground as quickly as possible. Steve knows that if he takes too long, everyone will get bored, and the game will be over. But Steve doesn't know the best way to get across without taking too long.
So, Steve thinks about the stationary-action principle. This is a fancy way of saying that he thinks about finding the best path, or the path with the least resistance, that will help him get to the other side of the playground as quickly as possible.
Steve decides to try a bunch of different paths. He walks straight across, runs in circles, zig-zags all over the playground, and even jumps over the swings.
Then, Steve uses the stationary-action principle to figure out which path is the best. He looks for the path where he uses the least amount of energy and where he goes the fastest.
In the end, Steve finds the path with the least resistance, and he and his friends use that path to get across the playground as quickly as possible.
So, the stationary-action principle helped Steve find the quickest path to reach his goal. Scientists and engineers use this same principle to help them figure out the best way to get things done, like building spacecraft or designing bridges.
To make it easy to understand, let's imagine you are playing a very fun game called "Follow the Leader". The leader (let's call him or her Steve) will lead you and your friends across a playground. Steve can walk, run, or even jump to get across.
Now, let's say that Steve wants to lead everyone across the playground as quickly as possible. Steve knows that if he takes too long, everyone will get bored, and the game will be over. But Steve doesn't know the best way to get across without taking too long.
So, Steve thinks about the stationary-action principle. This is a fancy way of saying that he thinks about finding the best path, or the path with the least resistance, that will help him get to the other side of the playground as quickly as possible.
Steve decides to try a bunch of different paths. He walks straight across, runs in circles, zig-zags all over the playground, and even jumps over the swings.
Then, Steve uses the stationary-action principle to figure out which path is the best. He looks for the path where he uses the least amount of energy and where he goes the fastest.
In the end, Steve finds the path with the least resistance, and he and his friends use that path to get across the playground as quickly as possible.
So, the stationary-action principle helped Steve find the quickest path to reach his goal. Scientists and engineers use this same principle to help them figure out the best way to get things done, like building spacecraft or designing bridges.