SIMPLIFIED: "5.3: Newton's First Law"

Link: https://phys.libretexts.org/Bookshelves/University_Physics/University_Physics_(OpenStax)/Book%3A_University_Physics_I_-_Mechanics_Sound_Oscillations_and_Waves_(OpenStax)/05%3A_Newton's_Laws_of_Motion/5.03%3A_Newton's_First_Law 

Note: The above image was taken from the original article.

I think that Newton’s Laws are a topic that countless people have heard of, but they can’t really fully explain. There is another article that Simplifying STEM has simplified regarding Newton’s second law, but this article is all about Newton’s first law.

Here is what Newton’s first law says: an object at rest stays at rest unless an external force interacts with that object, AND an object in motion stays in motion unless an external force is exerted on the object. Basically, if a ball is rolling, it isn’t gonna stop rolling until another force stops it. This force could be someone’s hand stopping the ball, or simplify friction force. When I say friction, think about it this way: if you roll a bowling ball across your carpet floor, it’s gonna stop rolling eventually, and the force acting on the bowling ball is friction. 

Similarly, an object at rest is gonna stay at rest unless something moves it. If you leave your calculator on the table, that calculator isn’t gonna start moving around unless you push it or pick it up; both pushing it and picking it up are examples of external forces. 

Newton’s first law also deals with something that is called inertia. Inertia is the ability for an object to resist any change or difference in motion or movement. For instance, a 50 kilogram dumbbell would have more inertia than a 10 kilogram dumbbell, because a 50 kilogram dumbbell is literally harder to move. It would have more inertia because it would resist movement more than the 10 kilogram dumbbell.

This whole idea of inertia is pretty confusing so here are some more real world examples. When you are laying down on a couch, your body doesn’t want to move because it’s already at rest. Therefore, in order to get your body to move, you use your arms or feet; these arms or feet involve your muscles acting as a force, and this force is what causes your body, which used to be at rest, to eventually be in motion. Here is another example: let’s say you are in a car that is driving on the highway. Suddenly, the driver SLAMS the brakes, and your body naturally tilts forward (the whole point of seatbelts is to catch you and prevent you from flying through the window when this happens lol). When these brakes are pressed, the brakes are a force bringing the car closer to rest. However, your upper body isn’t touching the car at all, so your upper body wants to keep moving forward, because remember, an object in motion wants to stay in motion. The seatbelts are the force that brings you back to rest.