StarCraft® II

Physics question to contemplate

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is frictionless acceleration possible? what about in space? there is no atmosphere to produce drag so i think it would be possible, although i haven't taken physics yet so i haven't a clue.
anyone?
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Posts: 1,489
Frinctionless Acceleration is impossible.
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Posts: 1,796
frictionless acceleration is a somewhat confusing term.

Acceleration is what happens with a force acts upon a mass. The equation is really F=ma, or to put it in the terms of acceleration it's a=F/m meaning if a force on an object is kept constant and the mass of the object increases, the acceleration decreases. If the force on an object increases while the mass remains constant, the acceleration increases. Friction acts as a "force" or F in the equation, although it's a negative force meaning it causes negative acceleration or "deceleration." So, yes frictionless acceleration is entirely possible, but that doesn't mean infinite acceleration is possible, if that's what you're getting at. There always needs to be a force acting on an object to cause acceleration.

Also, I think there's some confusion with acceleration and velocity. Velocity describes an object moving at a constant speed. Acceleration describes the rate at which the velocity of an object increases or decreases

Source: took a physics in engineering course
Edited by Tewks on 6/3/2011 1:06 AM PDT
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Posts: 1,027
if there is nothing to produce friction, there is nothing to exert force on to accelerate.

your hypothetically floating in a vacum and for some magically reason you havent exploded.
have fun jump or running with nothing to push off of.

im pretty sure that all makes sense in very very simple terms.

i could be wrong.
if anyone is a physics expert please prove me wrong, or prove me right.
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Posts: 1,796
if there is nothing to produce friction, there is nothing to exert force on to accelerate.

your hypothetically floating in a vacum and for some magically reason you havent exploded.
have fun jump or running with nothing to push off of.

im pretty sure that all makes sense in very very simple terms.

i could be wrong.
if anyone is a physics expert please prove me wrong, or prove me right.


A rocket ship in the vacuum of space has a force being exerted on it (the burning of the rocket fule) while there is nothing producing friction.
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Posts: 768
The thing is that space isn't empty, they're tonnes of very small particles and objects floating around that will have a minute effect on your acceleration. Gravity is a much bigger problem when speaking about kinematics and space travel however.
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Posts: 169
If you're just talking about friction outside the spaceship, for all practical purposes no. There is dust in space and that dust, however minute, generates friction.
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Posts: 1,901
"Frictionless acceleration" is like "Tromboneless running".

Both are possible, but neither term makes much sense.
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Posts: 2,306
using fictional tech, u make a small shell outside of space-time, and then expand spacetime behind u, and contract it in front. maybe using big magnets or sumthin

wth is ur friction-lesss acceleration for anyway?

also, kinda around wut tewks said, there is a speed limit on the universe, the speed of light. as matter approaches the speed of light, the matter's relative time approaches zero (time experienced). so u can't conventionally accelerate infinitely, b/c you would leave space-time.

there is a theoretical particle called a tachyon, whose speed MINIMUM is the speed of light. it always arrives at its destination before it leaves its location.

http://en.wikipedia.org/wiki/Tachyon

http://en.wikipedia.org/wiki/Faster-than-light
Edited by Fenix on 6/3/2011 5:18 AM PDT
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Posts: 3,473
My Queen frictionlessly Injects larva into Kerrigan's Hatchery all the time. Which spawn eggs, that eventually accellerate into Zerglings.
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Posts: 1,043
06/03/2011 05:07 AMPosted by Fenix
there is a theoretical particle called a tachyon, whose speed MINIMUM is the speed of light. it always arrives at its destination before it leaves its location.


It takes light 8 minutes to reach earth from the sun. Therefore, at minimum speed, a tachyon does NOT arrive at its destination before it leaves its location.
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Posts: 3,492
06/03/2011 05:34 AMPosted by AdmralAckbar
there is a theoretical particle called a tachyon, whose speed MINIMUM is the speed of light. it always arrives at its destination before it leaves its location.


It takes light 8 minutes to reach earth from the sun. Therefore, at minimum speed, a tachyon does NOT arrive at its destination before it leaves its location.

Our shields can not repel tachyons of this magnitude!
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Posts: 1,043
06/03/2011 05:36 AMPosted by IAreLemons
Our shields can not repel tachyons of this magnitude!

See people always drop the "its a trap" reference, but rarely do i get this.... good quote drop man.

Also, if you look up, "Its a Frappe" (google images), some coffee shop somewhere has a picture of their daily chalkboard. It has a perfectly drawn Admiral Ackbar and it says.

"Your barista for the day is 'Admiral Ackbar'....

We cannot repel flavor of this magnitude!
Edited by AdmralAckbar on 6/3/2011 5:38 AM PDT
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Posts: 2,610
Friction is an opposite force created by a surface on an object moving on it.

Friction(---Object---> Force (i.e. some1 pulling on it)

If the force done by the ---) arrow is < than the force done by the ---> arrow then the sum of the forces > 1 = acceleration according to Newton's Law:

sum of Forces = mass x acceleration

An object with a mass not moving as a certain ''inertia''. To break this inertia you must apply a force on it to induce an acceleration.

In space where it's empty, an object still has the same inertia. When you apply a force on the object it'll still have an acceleration = force/mass

The difference is that since there's no ''surface'' or ''matter'' surrounding the orject it won't apply a counterforce in the opposite direction, or friction.

So yes frictionless acceleration can take place in empty environemment because the acceleration still requires a force to break the object's inertia.

I tried to keep it simple but it's really easier to explain with a sketch and math symbols.

Edit for those confused about speed of light:

According to Einstein's relativity, an object gains mass the faster it moves

mass moving = y x mass not moving.

Y tends towards infinite as you approach the speed of light. It means at the speed of light

force = mass x acceleration mass = infinite force = infinite -> impossible

to go from 0,999999c to 1c C being to speed of light you'd need an infinite amount of force to accelerate the few meters/seconds you need to obtain it making it impossible.

The reason photons (particles of light) can travel at the speed of light is because when not moving they their mass is 0 meaning that you need 0 amount of force for them to reach infitite (according to Newton's equation) acceleration.

We now know that Newton's equation isn't 100% correct because the maxed speed is capped at 300 000 km/s for the world to behave as we see it.
Edited by Nonamesleft on 6/3/2011 5:49 AM PDT
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Posts: 334
It's entirely possible. Why wouldn't it be? Friction assists in 'deceleration' (and in acceleration of something trying to change direction.. but technically deceleration isn't a real term anyways), but is not required for either.

06/03/2011 01:53 AMPosted by MGDocHoliday
no such thing as a complete vacuum, so no.


Of course there is such thing as a complete vacuum. I assume what you're talking about is quantum fluctuations in empty space? Matter isn't fluctuating into every little bit of space all the same time. If it were, space would look like a giant blob of quantum foam. It looks empty because 99.9999...% of it is at any given time. If I took a square inch of "space" and said we should analyze it at the exact moment... right... NOW.. Chances are that it would have been a complete vacuum.

Even given matter fluctuations, space is still almost entirely empty. The average size of a space shuttle is ~150ft x 30ft x 30ft. If the shuttle is traveling through empty space this size, there are 3 possibilities.

1. Overwhelmingly likely: The space in 150x30x30 has no relevant fluctuation of matter, and the ship is accelerating in empty space.
2. Rare: A particle fluctuates into being inside this spaceships area, but it is either some nanometers-> feet away from the hull-- or it collides at such an angle that it causes no friction to the shuttle.
3: Overwhelmingly rare: A particle is created and hits at just the right angle as to cause a small amount of friction.

Even in situation 3, the particle is so small and exists for such an incomprehensibly short time, that the effects are about the same as you shining a flashlight is going to have on the Andromeda galaxy.

Even if there were no such thing as empty space, frictionless acceleration would STILL be possible. Anyone involved in physics knows that just because a situation doesn't occur, doesn't mean that relevant laws don't exist for that situation.
Edited by Ninefold on 6/3/2011 6:35 AM PDT
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Posts: 97
I have a degree in Engineering Physics... 90% of what is said above is correct, and the summary is that yes... it is possible.

Rocket fuel has mass and energy being ejected from the back, and thus us the equal and opposite reaction to the rocket moving forward. Magnetic fields, gravity, and other forces can also cause acceleration in the 'almost perfect' vacuum of space.



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Posts: 1,704
I'm no scientist but I wonder if the future of travel will have anything to do with manipulating magnetic fields or somethin
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