# Inertia

Imagine if inertia was just removed. How would everyday activities be changed? How about Rollercoasters and driving cars. How would the universe function if inertia was unexistent?

Everything would move at the speed of light

>Earth stops spinning
>Stops orbiting
>Wind stops
>Water flow stops
Yeah you die basically

You wouldn't be able to move your arms, fingers, or probably any limb short of your eyes. Everything would have to be done with pure torque, and we aren't designed for pure torque. Literally every movement would feel like you were trying to lift the universe or something.

Take Newton's equations, and substitute F =mv. There, inertia no longer exists, work out the results for yourself.

Would make no fucking sense. Take two frames of reference [math]\mathscr R[/math] and [math]\mathscr R'[/math] such that [math]\mathscr R'[/math] has a uniform linear motion relative to [math]\mathscr R[/math]. Place yourself in [math]\mathscr R[/math] and let [math]M[/math] be a solid. Push it to give it movement in both [math]\mathscr R[/math] and [math]\mathscr R'[/math]. Stop pushing it. How is it supposed to stop in both [math]\mathscr R[/math] and [math]\mathscr R'[/math]?

>F=mv
wut ?

Without inertia, there is no coherent physics, which kinda puts a damper on your thought experiment.

>damper
Now that you mentioned damping, let's ask an opposite question: what if friction would be removed, so that moving objects would need to be stopped explicitly by some specific counterforce, rather than just being decelerated by surrounding particles? What if inertia was given free reign, rather than being dampened by friction?

you get shit happening

But shit is happening even now, with both inertia and friction existing.

>uniform linear motion

the "uniform linear motion" thing is derived from inertia

no inertia = "uniform linear motion" is irrelevant

You main issue is that every loose object is going to keep sliding around. Cars and people are the obvious things, but I expect the most interesting effect would be in topsoil and bodies of sand. With no friction they lose their rigidity, turning into something similar to a liquid. Anything not attached to the continental plate would flow out to sea and settle at the lowest point it could reach, taking trees, buildings and anything else with it. With no friction there's also nothing to stop the wind, so I would expect the airspeed to reach absurd levels quite quickly.

Of course, with no friction there's little holding the continental plates in place. Earthquakes will become commonplace, although this won't be much of an issue at first as there's not going to be anything left to topple over.

I'm not sure what would happen after this. The problem with removing friction is that you remove the main way of turning motion into heat. Taking that away means motion will just continue to build until the planet shakes itself apart, unless there's some other way to slow things down.

no inertia = no inertial mass = no gravitational mass = pure energy = EM waves

if you remove inertia you have a world of electromagentic waves

So of gravity, inertia, and friction, it's all three which contribute to the stability of various things.

Everything would act as if they would be moving through an extremely viscous liquid.
For particles with low Reynolds number inertia is negligible.
Moving would be a pain in the ass, and require constant force.

This is a nonsensical question and most of the answers in this thread show a profound lack of understanding of what inertia is.

Inertia is just the recognition of the fact that any "thing" will remain to be as it is, until another force acts on it.

You don't gain or lose inertia. It's not a measurable quantity, or quality.
You are only moving while accelerating.
When you are no longer accelerating, you are no longer moving.
If your car hits a low barrier and you are thrown through the windshield, it is equally correct to say that you were standing still, a barrier approached and impacted your car, which forced the car backward and the windshield into your face.

There is no actual quality of inertia that makes this so. It's just a recognition of the fact that, from any particular point of reference, something that appears to be moving continues to do so, and something that is not, does not.
You might as well ask "what would the universe be like if space was backwards"
The question is nonsense.

>It's not a measurable quantity, or quality.

yes it is, if you measure inertial mass

yes it is, if you measure inertial forces

When you understand your mistake, it'll be one of those epiphanies that surprises you about how narrow your understanding was.

Yeah, I took a shit yesterday and both inertia and friction were operating normally

You came off as enlightened until
>You are only moving while accelerating
at which point you just come off as a try-hard idiot trying to sound intelligent. One could say that you show a profound lack of understanding of what inertia is.

Smoke more weed until it makes sense.

No. It is a stupid and incorrect way to describe motion.

Look at the (correct) resolution of the twin paradox, in the special case of the "space" twin returning to compare clocks.

In the space twin's reference frame, you can either say the earth is moving away at first, at which point the twin accelerates to catch up, OR you can say that the space twin was already moving away from the earth, and then decelerates in order to allow the earth to catch up. Both frames are equally valid for the space twin, but note that one frame involves acceleration for the space twin at the first half of the encounter, while the other frame, for the same twin, involves acceleration at the second half.

Contradiction. Bad definition. Motion is defined by relative velocity, not by acceleration.

what if c was 10 km/h.

...

holy shit you're right

It's velocity instead of acceleration, because without inertia acceleration is impossible

Literally your car would not be able to stop from crashing into that barrier at 95 mph.

You ever seen gifs like this?

So yea, like this.

OK, so what if friction was generally reduced by many orders of magnitude, but would be non-zero, so that a car could coast for miles on a flat road, but brakes would still work? Would much more energy then need to be used to stop an object from moving, so that the total energy expense to accelerate an object an then bring it to a halt again would be approximately the same as with normal friction?