10 Examples of Inertia

We have all noticed at times that if we ride while standing on the bus and it brakes suddenly, our body tends to “continue traveling”, which forces us to quickly grab onto a firm element inside the bus so as not to fall.

This happens because bodies tend to maintain their state, of rest or of movement, unless they are subjected to the action of a force. Physics recognizes this phenomenon as “inertia”.

The inertia It is the resistance that matter opposes to modify its state of rest or movement, and that state is only modified if a force acts on them. It is said that a body has greater inertia the greater resistance it opposes to modify its state.

Types of inertia

Physics distinguishes between mechanical inertia and thermal inertia:

  • Mechanical inertia. It depends on the amount of dough. The more mass a body has, the more inertia it has.
  • Thermal inertia. It quantifies the difficulty with which a body changes its temperature when it comes into contact with other bodies or when it is heated. Thermal inertia depends on the amount of mass, thermal conductivity, and heat capacity. The more massive a body is, the less thermal conductivity it has or the more heat capacity it possesses, the greater its thermal inertia.

Newton’s first law

The idea of ​​inertia has been embodied in Newton’s first law or law of inertia, according to which if a body is not subject to the action of forces, it will maintain its speed in magnitude and direction at all times.

However, it is interesting to note that before Newton, the scientist Galileo Galilei had already raised this concept by confronting the Aristotelian point of view in his work Dialogues on the two great systems of the world, Ptolemaic and Copernican, dating from 1632.

There he says (in the mouth of one of his characters) that if a body were to slide along a smooth and perfectly polished plane, it would maintain its movement ad infinitum. But if this body were to slide on an inclined surface, it would suffer the action of a force that could cause it to accelerate or decelerate (depending on the direction of the inclination).

So Galileo already envisioned that the natural state of objects is not exclusively that of rest, but also that of a rectilinear and uniform motion, as long as there are no other forces acting.

Associated with this physical concept, when describing human behavior, the other meaning of the term inertia appears, which is applied to those cases in which people do nothing about something due to a matter of laziness, attachment to routine, comfort or simply by letting themselves be as they are, which is often the easiest.

Examples of inertia in everyday life

Many everyday situations account for the physical phenomenon of inertia:

  1. Inertial seat belts. They only lock if the body continues to move when there is a sudden stop.
  2. Washing machine with spin. The drum of the washing machine has holes so that when you spin to spin the clothes, the drops of water that have a certain speed and direction continue in their movement and pass through the holes. It is said then that the inertia of the drops, the state of movement that they possess, helps to remove the water from the clothes.
  3. Catch the ball in soccer. If an archer does not stop with his arms the ball applied by the striker of the opposing team, there will be a goal. The ball in motion, due to its inertia, will continue to travel towards the inside of the goal unless a force, that of the goalkeeper’s hands in this case, prevents it.
  4. I pedal a bicycle. We can advance with our bicycle a few meters after having pedaled and stop doing it, the inertia makes us advance until the friction or friction exceeds it, then the bicycle stops.
  5. Hard-boiled egg test. If we have an egg in the refrigerator and we do not know if it is raw or cooked, we place it on the counter, we turn it carefully and try to stop it with a finger: the hard-boiled egg will stop immediately because its content is solid and forms a whole with the shell, so that if you stop the shell, so does the inside. However, if the egg is raw, the liquid inside does not stop immediately along with the shell, but will continue to move for a while longer due to inertia.
  6. Remove a tablecloth and leave what is above resting on the table, in the same place. A classic magic trick based on inertia; To get it right, you have to pull the tablecloth down and the object should be rather light. The object resting on the tablecloth opposes the change in its state of movement, it tends to remain still.
  7. The shots with effect in billiards or pool. When trying to achieve the caroms, taking advantage of the inertia of the balls.