This means that all bodies tend to remain in the state they are initially in, that is, if they are in motion, they will tend to remain in motion until someone or something stops them; if they are immobile, they will tend to remain immobile until someone or something breaks their state and makes them move.
Currently, this statement may seem a little obvious, but it should not be forgotten that this discovery, as well as other very relevant ones, among which the law of universal gravitation and the studies on the decomposition of white light into different colors, made by Isaac Newton approximately 450 years ago.
Newton’s Laws, including this Law of Inertia, in addition to the Law of Interaction and Force, and the Law of Action and Reaction – which together form Newton’s laws of Dynamics – came to scientifically explain how objects or bodies with mass act and react the presence or absence of forces exerted on them.
Examples of the law of inertia
1- The car that stops abruptly
The most graphic and everyday example that this law explains is the movement our body makes when we enter a car at a constant speed and come to an abrupt stop.
Immediately the body tends to continue in the direction the car was going, and is thrown forward. This movement will be smooth if the car comes to a smooth stop, but it will be much more violent if you brake hard.
In extreme cases, such as a collision with another vehicle or object, the force exerted on the object (car) will be greater and the impact will be much stronger and more dangerous. That is, the body will maintain the inertia of the movement it brought.
The same is the opposite. When the car comes to a complete stop and the driver accelerates sharply, our bodies tend to stay as they were (ie at rest) and that’s why they tend to back off.
2- Moving a stationary car
When trying to push a car, it is very difficult at first, because due to inertia, the car tends to stand still.
But since it is possible to set it in motion, the effort that must be made is much less; since then, inertia keeps it moving.
3- The athlete who cannot stop
When an athlete tries to stop his run, it takes several meters to come to a complete stop, due to the inertia produced.
This is most clearly seen in track competitions such as the 100 meter run. Athletes continue to advance far beyond the goal.
4- Football theater … or not
Theatrical takedowns between players on both teams often take place in a football match. Often these drops can seem exaggerated when one of the athletes takes several turns on the grass after impact. The truth is, it’s not always about histrionics, but about the law of inertia.
If a player is running at high speed across the field and is rudely intercepted by someone on the opposing team, he is actually interrupting the rectilinear movement he was carrying, but his body tends to continue in the same direction and at that speed. That’s why the spectacular crash takes place.
5- The autonomous bicycle
Pedaling a bicycle allows it to keep moving for several meters without having to pedal, thanks to the inertia produced by the initial pedaling.
6- Up and down
Roller coasters can climb steep slopes thanks to the inertia produced by the previous steep descent, which allows them to accumulate potential energy to climb again.
7- Trick or science?
Many tricks that seem surprising are actually simple demonstrations of Newton’s First Law.
This is the case, for example, of the waiter who can tear the tablecloth off the table without falling off the objects placed on it.
This is due to the speed and force applied to the movement; objects at rest tend to stay that way.
8- Question of technique
A deck of cards on a finger (or in a cup) and, in the deck, a coin. By a quick movement and force exerted on the deck, it will move, but the coin will remain immobile in the finger (or it will fall into the cup).
9 – Boiled egg vs raw egg
Another experiment to check the Law of Inertia can be done by taking a hard-boiled egg, rotating it on a flat surface and stopping the movement with your hand.
The hard-boiled egg will stop immediately, but if we do exactly the same experiment as before with a raw egg, trying to stop the egg’s rotational movement, we will see that it continues to rotate.
This is explained by the fact that the raw white and yolk are loose inside the egg and tend to keep moving when force is applied to stop it.
10- Block Tower
If you build a tower with several blocks and hit the bottom block (the one that supports the weight of others) with a hammer, you can remove it without the rest falling, taking advantage of the inertia. Bodies that still tend to remain immobile.
11- Billiards billiards
In billiards, the player tries to make carambolas by hitting the balls with the cue or with other balls. Until then, the balls will remain stationary with nothing to disturb them.
12- Space travel
Ships that launch into space will maintain a constant velocity indefinitely, as long as they are far away from gravity and have no friction whatsoever.
When an athlete kicks a ball, whether it’s football, rugby or another sport, he uses his muscles to generate a force that allows the ball to move when it’s at rest. The ball will only be stopped by the friction of the earth and gravity.
The modern world could not be conceived as it is, were it not for the very important contributions of this Briton, considered by many to be one of the most important scientific geniuses of all times.
Perhaps without realizing it, many of the acts we perform in our everyday life constantly explain and confirm Newton’s theories.
In fact, many of the “tricks” that often surprise young and old at fairs or television programs are nothing more than proofs and a phenomenal explanation of the laws of dynamics, especially this first law of Newton or Law of Inertia.
Having already understood that, if no other body acts on it, it remains stationary (at zero velocity) or moves indefinitely in a straight line with constant velocity, it is also necessary to explain that all movement is relative, as it depends on the subject who observes and describes that movement.
For example, the stewardess walking down the aisle of an in-flight plane, delivering coffee to passengers, is walking slowly from the point of view of the passenger who is waiting in their seat for the coffee to arrive; But for someone watching the plane fly from the ground, if he could see the stewardess, he’d say he’s moving at great speed.
Thus, motion is relative and basically depends on the point or frame of reference used to describe it.
The inertial frame of reference is one used to observe bodies on which no force acts and therefore remains immobile and, if it moves, will continue to move at a constant speed.