What the heck is inertia anyway?

• quasi426
In summary, inertia is the resistance of an object to be accelerated or decelerated. The principle of relativity says that the laws of physics are the same in a constantly moving reference frame. This is why you can do a physics experiment in the lab and analyse it without having to take into account the motion of the lab around the Earth, or Earth around the Sun, or the Sun around the galaxy, and so on.

quasi426

HI, I never really gave it much thought, but does anyone have an explanation for inertia at the molecular or atomic level. I think that it takes time for the force or energy to travel throughout the molecules and/or atoms of a body and that is why it continues to stay in motion. Can anyone explain it better, or more correct.

Nobody really knows why inertia exists. Inertia is quantified by the thing we call "mass", which gives the resistance of an object to being accelerated (a = F(net)/m).

Why should things with mass resist being accelerated? That is a complete mystery. An equivalent question is simply "Why does mass exist?", and nobody knows the answer to that one, either.

Hi quasi,
The principle of relativity says that the laws of physics are the same in a constantly moving reference frame. This is why you can do a physics experiment in the lab and analyse it without having to take into account the motion of the lab around the Earth, or Earth around the Sun, or the Sun around the galaxy, and so on.

This means that the tendency for an object to stay in motion is exactly the same as the tendency for an object to remain at rest... there is no real difference between the two. So, if you're happy to accept that an object at rest should tend to remain at rest, then the inertia of an object in motion needs no further explanation.

Pete

I was always taught this definition :

Inertia is the property of matter to resist accleration or deceleration, where accelertation and deceleration are of course, any motion which is not in a straight line and with constant velocity.

Which made me think, is inertia the resistance of a bodyto have unbalanced forces acting upon it? As to turn an object, or to stop it having constant velocity, one must change the forces acting on it.

Regards,

Ben

BenGoodchild said:
Which made me think, is inertia the resistance of a bodyto have unbalanced forces acting upon it? As to turn an object, or to stop it having constant velocity, one must change the forces acting on it.

Maybe you just chose your words poorly but just in case:
If some forces act upon an object it does not move at a constant velocity or unless the forces cancel each other out.

If you want a definition of the moment of inertia I when doing rigid-body physics, here it is : the I expresses how mass is distributed over the entire object's volume. When a rigid body (thus no point particle) moves down, the acceleration does not depend on the mass, the volume but the way mass is distributed over the volume. When you are going downhill with your bicycle, you will go faster if you lean over, right (let's neglect air resistance)? Well, you know the reason.

The I is also called mass-tensor and i am sure you all know what a tensor is and why it is useful in physics

regards
marlon

quasi426 said:
HI, I never really gave it much thought, but does anyone have an explanation for inertia at the molecular or atomic level. I think that it takes time for the force or energy to travel throughout the molecules and/or atoms of a body and that is why it continues to stay in motion. Can anyone explain it better, or more correct.
Inertia is that property of a body which resists changes in momentum.

Pete

Hey just think that inertia is just mass

Hey there ! What i mean is that inertia is something that is used in rotational motion and mass is used in place of inertia in translational motion. Ex. F=m.a(i.e. For translational motion) and Tau=inertia . alpha(for rotational motion) . For mass we usually use inertia in rotational dynamics.

1. What is inertia?

Inertia is a property of matter that describes an object's resistance to change in its state of motion. It is the tendency of an object to remain at rest or in uniform motion unless acted upon by an external force.

2. How does inertia affect everyday objects?

Inertia affects everyday objects in many ways. For example, when you push a book on a table, it will not move unless you apply enough force to overcome its inertia. Inertia also explains why objects continue to move in a straight line unless acted upon by a force, such as a ball rolling down a hill.

3. How is inertia related to Newton's First Law of Motion?

Inertia is directly related to Newton's First Law of Motion, also known as the law of inertia. This law states that an object at rest will remain at rest, and an object in motion will continue to move in a straight line at a constant speed, unless acted upon by an external force. Inertia is the reason why objects follow this law.

4. How does mass affect inertia?

The greater the mass of an object, the greater its inertia. This means that objects with larger masses require more force to change their state of motion compared to objects with smaller masses. For example, it is much harder to push a car (which has a larger mass) than it is to push a bicycle (which has a smaller mass).

5. How is inertia important in space travel?

In space travel, inertia plays a crucial role in the movement of objects. To change the direction or speed of a spacecraft, a force must be applied to overcome its inertia. Inertia also explains why astronauts continue to float in space unless acted upon by a force, such as the force of a spaceship or space suit. Understanding inertia is crucial for accurately controlling the movement of spacecraft in space.