Newton’s first law , also called the Law of Inertia, states that every body remains at rest or in uniform and rectilinear motion unless another body intervenes and acts on it.
This means that all bodies tend to stay in the state in which they are initially, that is, if they are in motion they will tend to remain in motion until someone or something stops them; if they are still, they will tend to remain still until someone or something breaks their state and makes them move.
In our days this statement may seem somewhat obvious, but it should not be forgotten that this discovery, as well as others that are also very relevant, among which we can mention the law of universal gravitation and the studies on the decomposition of white light in different colors were made by Isaac Newton about 450 years ago.
Newton’s laws, which include this Law of Inertia, in addition to the Law of Interaction and Force, and the Law of Action and Reaction – and which together make up Newton’s laws of Dynamics – came to explain scientifically, how objects or bodies with mass act and react to the presence or not of forces exerted on them.
Examples of the Law of Inertia
Examples of the Law of Inertia
1- The car that brakes abruptly
The most graphic and everyday example that explains this law is the movement that our body makes when we are in a car at a constant speed and it stops abruptly.
Immediately the body tends to continue in the direction the car was taking, so it is thrown forward. This movement will be smooth if the car stops smoothly, 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 that it brought.
The same happens to the contrary. When the car is at a complete stop, and the driver accelerates sharply, our bodies will tend to remain as they were (that is, at rest) and that is why they tend to roll back.
2- Moving still car
When trying to push a car, it is very difficult at first, because due to inertia, the car tends to stay still.
But once it is able to put it in motion, the effort that must be made is much less, since then, inertia makes it keep moving.
3- The athlete who cannot stop
When an athlete tries to stop his run, it takes him 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 sprint. Athletes continue to advance well beyond the goal.
4- Football theater … or not
In a soccer game, theatrical falls often happen between players from both teams. Many times these falls can seem exaggerated, when one of the athletes takes several laps on the grass after the impact.
The truth is that it does not always have to do with histrionics, but with the Law of Inertia.
If a player comes running at high speed across the field, and is roughly intercepted by someone from the opposing team, he is actually interrupting the rectilinear movement that he was carrying, but his body will tend to continue in that same direction and at that speed. That is why the spectacular fall happens.
5- The autonomous bicycle
Pedaling a bicycle allows it to continue advancing several meters without having to pedal, thanks to the inertia produced by the initial pedaling.
6- Go up and down
Roller coasters can go up steep slopes thanks to the inertia produced by the previous steep downhill, which allows you to accumulate potential energy to go up 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 pull a tablecloth off a table without the objects placed on it falling out.
This is due to the speed and force applied to the movement; objects that were at rest tend to stay that way.
8- Question of technique
A deck on a finger (or on a glass) and, on the deck, a coin. By means of a rapid movement and force exerted on the deck, it will move, but the coin will remain still on the finger (or it will fall into the glass).
Cooked egg vs raw egg
Another experiment to check the Law of Inertia can be done by taking a boiled egg and spinning it on a flat surface and then stopping the movement by hand.
The boiled egg will stop immediately, but if we do exactly the same experiment as above with a raw egg, when we try to stop the rotating movement of the egg, we will observe that it continues to rotate.
This is because the raw white and yolk are loose inside the egg and tend to keep moving once force is applied to stop it.
10- Block tower
If a tower is made with several blocks and the bottom block (the one that supports the weight of the others) is hit hard with a mallet, it will be possible to remove it without the rest falling, taking advantage of the inertia. Bodies that are still tend to stay still.
11- The billiard caroms
In billiards, the player seeks to perform caroms by hitting the balls with the cue or with other balls. Until then, the balls will stand still with nothing to disturb them.
12- Space travel
The ships that are launched into space will maintain a constant speed indefinitely as long as they are away from gravity and do not have any type of friction.
When an athlete kicks a ball, be it soccer, rugby or another sport, the athlete uses his muscles to generate a force that allows the ball to move 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 geniuses
most important scientists of all time.
Perhaps without realizing it, many of the acts that we perform in our daily lives constantly explain and confirm Newton’s theories.
In fact, many of the “tricks” that tend to astonish young and old at fairs or television shows are nothing more than the verification and a phenomenal explanation of the laws of dynamics, especially this first law of Newton or Law of Inertia.
Having understood that if no other acts on a body, it will remain still (at zero speed) or indefinitely moving in a straight line with constant speed, it is also necessary to explain that all movement is relative, since it depends on the observing subject and describe the movement.
For example, the flight attendant who walks down the aisle of an in-flight plane handing out coffee to the passengers, walks slowly from the point of view of the passenger who waits in his seat for the arrival of his coffee; But for someone who watches the plane flying from the ground, if he could see the flight attendant, he would say that it is moving at great speed.
Thus, the movement is relative and depends, basically on the point or reference system that is taken to describe it.
The inertial reference system is the one used to observe those bodies on which no force acts and, therefore, remains still, and if it moves, it will continue to move at a constant speed.