Can a Vacuum in Space Create Drag on Moving Objects?

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Discussion Overview

The discussion revolves around the concept of drag in a vacuum, particularly whether a vacuum in space can create drag on moving objects. Participants explore the mechanics of force application in a vacuum, the principles of rocket propulsion, and the interactions between objects in space.

Discussion Character

  • Debate/contested
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • Some participants question whether a vacuum can create drag on objects moving through it, suggesting that space cannot be mechanically interacted with like a gas.
  • Others argue that while a vacuum does not provide drag, forces can still be applied in space, as demonstrated by rocket propulsion.
  • One participant claims that throwing an object in a vacuum would not result in the object moving away due to the equal and opposite reaction, which is challenged by others who assert that the forces do not cancel out as they act on different bodies.
  • There is a discussion about the mechanics of rockets, with some participants asserting that the mass flow of exhaust gases is what propels the rocket, while others question how this can occur without resistance in a vacuum.
  • Some participants introduce the concept of effort and resistance forces, debating their relevance in the context of rocket propulsion and motion in a vacuum.
  • One participant compares the operation of a rocket to that of a gun, questioning how the rocket can function without a second body to push against, while others clarify that the exhaust itself provides the necessary interaction.
  • Concerns are raised about the necessity of resistance for forces to do work, with some participants asserting that forces can still act in a vacuum without traditional resistance.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the nature of drag in a vacuum or the mechanics of force application in space. Multiple competing views remain regarding the role of resistance and the functioning of rockets in a vacuum.

Contextual Notes

Participants express uncertainty about the definitions and implications of resistance and effort forces in the context of motion in a vacuum. The discussion includes various assumptions about the mechanics of force interactions that are not fully resolved.

  • #31
F= reaction inside rocket
m= gas leaving the rocket
a= relative motion
By definition of joules second law gas cannot exist in a vacuum without a containing force therefore do no work which cancels ""m"" which negates ""a"" the rocket now is only subject to it own inertia and velocity...the propellant cannot interact with the vacuum so fails to push.. A soon as the rocket leaves the atmospheric envelope the rocket cannot do work
 
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  • #32
Forget the rocket for a second. It complicates things with gases and mass flows. Do you agree that if you are in a vacuum and you throw your shoe away, both you and the shoe will move away from each other?
 
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  • #33
Newtonforce; Are you asking or telling? Obviously that must be wrong, since rockets work in a vaccum. Rather than following your own line of logic to a wrong answer, you'd be better off trying to absorb what we are telling you.
 
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  • #34
""Do you agree that if you are in a vacuum and you throw your shoe away, both you and the shoe will move away from each other?""

no i dont...on the planet my feet are stationary and i can use leverage from friction allowing my body to apply force to shoe...shoe resists my applied force and moves away from me..
In space vacuum i have no leverage to apply a force in a specific direction and the shoe will not resist my applied force ...a lot of effort with no outcome..
 
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  • #35
Newtonforce said:
...shoe resists my applied force and moves away from me..
In space vacuum i have no leverage to apply a force in a specific direction and the shoe will not resist my applied force ...
Why does the shoe resist your applied force on earth, but not in space? What is the nature of the "resistance" you are referring to? What about a=f/m?
 
  • #36
zero g...you have all seen ISS antics ...liquid ping pong...floating foods people moving around the space station...if the ISS wasnt doing mach 20 none of those things would be possible...on the space station 400km in space there is still a great deal of gravity and so forward velocity stops ISS coming back to earth...
so the nature of the resistance I am referring to is zero resistance...
me in space at rest floating ...how is it possible to apply force to another body if I am not fixed or immovable? any force i apply will be negated instantly by the equal and opposite reaction force..shoe no move
 
  • #37
Gravity pulls objects down. When you throw a shoe sideways, gravity is not resisting that. And if you throw a shoe up, the force you apply is much greater than the force of gravity on the shoe.

Objects in orbit still resist acceleration via a=f/m

Please read this link on Newton's laws of motion:
http://csep10.phys.utk.edu/astr161/lect/history/Newton3laws.html

You will notice that gravity is not part of the laws of motion.
 
  • #38
Newtonforce said:
"no i dont...on the planet my feet are stationary and i can use leverage from friction allowing my body to apply force to shoe...shoe resists my applied force and moves away from me..
In space vacuum i have no leverage to apply a force in a specific direction and the shoe will not resist my applied force ...a lot of effort with no outcome..
You don't need leverage do apply a force. In space, away from gravity, if you push a body it'll push you back with the same force and you both fly apart. You don't need any surface or medium to cling on to for motion.
.
.
EDIT: Does the following question encapsulate your confusion-
" On Earth were need a fictional surface to walk, or for a car to move. Since there is no surface in a vacuum, how to bodies move in space?"
 
  • #39
""The reciprocal of 0 force is 0 force. The equal and opposite reaction to 0 would be 0.

it makes perfect sense to me..to say the shoe will not leave my hand...as i throw the shoe the mechanical force created in my arm equaly applies onto the shoe and the opposite direction of my effort cancelling each other..shoe no move...

: If there were no gravity, and if the air did not impede the motion of bodies, then anybody will continue its given motion with uniform velocity in a straight line.

: Every body under the sole action of its innate force moves uniformly in a straight line indefinitely unless something extraneous hinders it.

: Every body perseveres in its state of being at rest or of moving uniformly straight forward except insofar as it is compelled to change its state by forces impressed.

how did the shoes state change if the forces impressed are equal and opposite
 
  • #40
Newtonforce said:
as i throw the shoe the mechanical force created in my arm equaly applies onto the shoe and the opposite direction of my effort cancelling each other..shoe no move...

Again, this is not true, and again, you don't understand Newton's third law. This thread is getting nowhere.
 
  • #41
Newtonforce said:
it makes perfect sense to me..to say the shoe will not leave my hand...as i throw the shoe the mechanical force created in my arm equaly applies onto the shoe and the opposite direction of my effort cancelling each other..shoe no move...
It doesn't matter what makes sense to you. Only thing that matters is what actually happens. The shoe will leave your hand and fly away. ( I think this thread is going to be locked soon).
 
  • #42
no the shoe is getting nowhere...how can my force be applied to the shoe without leverage or resistance..
how can you apply a mechanical force to the vacuum...me throwing a shoe needs me to anchor to something to apply force ...to over come its resistance ...
 
  • #43
See the edit in post #38.
 
  • #44
Newtonforce, I don't know what you are after here: you are now arguing that you can't throw a shoe. Please do me a favor: take off your shoe and throw it. Did you succeed in throwing it? So, why are you arguing a line of logic that you know is wrong and ignoring the help we are giving you? The others are right: this is going nowhere and will be locked soon if you don't put forth a better effort to learn.
 
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  • #45
how can a force be applied to another object in space vacuum if there is no anchor or leverage or external resisting forces?
my arm throws my body recoils from my arm and the shoe recoils from my hand that is connected to my arm we move as far as my arm is long and that's it no further
 
  • #46
what is the formula that describes how a mechanical force interacts with a vacuum?
 
  • #47
Newtonforce said:
what is the formula that describes how a mechanical force interacts with a vacuum?
What's the Frequency, Kenneth?
 
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  • #48
Newtonforce said:
what is the formula that describes how a mechanical force interacts with a vacuum?
Mechanical forces are interactions between "objects". So your question makes no sense.

When you throw your shoe there is a net force (from your hand) on the shoe. It accelerates.

True, the shoe exerts an equal and opposite force on you, but so what?
 
  • #49
A.T. said:
What's the Frequency, Kenneth?
Nice one :smile:
 
  • #50
""Mechanical forces are interactions between "objects". So your question makes no sense.""

that is perfect!
space vacuum is not an object...how can any force be applied to it..ie the force of my mass moving another mass..?
 
  • #51
Newtonforce said:
how can a force be applied to another object in space vacuum if there is no anchor or leverage or external resisting forces?
Please repeat back to me what I told you in post #30 or post #37.
 
  • #52
Newtonforce said:
space vacuum is not an object...how can any force be applied to it.
It cannot. To have a force applied to a vacuum is a meaningless statement.

Newtonforce said:
ie the force of my mass moving another mass..?
Nothing to do with a vacuum: you have one mass (you) exerting a force on another mass (the shoe). So? Nothing in here about exerting a force on a vacuum, whatever that might mean.
 
  • #53
Newtonforce said:
how can a force be applied to another object in space vacuum if there is no anchor or leverage or external resisting forces?
my arm throws my body recoils from my arm and the shoe recoils from my hand that is connected to my arm we move as far as my arm is long and that's it no further
Yes, your arm accelerates the shoe in one direction, and you will accelerate in the opposite direction if you are floating in space.
When the shoe is released you and the shoe will no longer be accelerating but will continue moving apart in opposite directions at a fixed velocity
 
  • #54
for me to apply a force i must be anchored...ISS mach 20 orbit velocity creates an artificial point of resistance..people can push of the craft hull and the space station stays anchored...if the ISS was in deep space without forward velocity if you pushed the craft it would move away from you as far as you from it...but it would not be able to go one mm further than your arms reach...you cannot move the object any further than net force applied which is equal and opposite to both bodies canceling each others acceleration
 
  • #55
Newtonforce said:
than net force applied which is equal and opposite to both bodies canceling each others acceleration

It. Does. Not. Cancel. Whether you like it or not. Please learn facts.
 
  • #56
Newtonforce said:
for me to apply a force i must be anchored..
Not true.

Newtonforce said:
.you cannot move the object any further than net force applied which is equal and opposite to both bodies canceling each others acceleration
So, since every mechanical force is accompanied by an equal and opposite force, you must agree that nothing can possibly accelerate. Right? That seems to be how you are thinking. (Which is wrong, of course.)
 
  • #57
So if you're in the vacuum of space and you, say slap a ball (instead of throwing it), you're saying that the ball would stick to your palm, instead of accelerating forward from the slap?

What about if you had a slingshot and you shot off a rock with it in space. You're saying the rock would stick to the rubber-band in space but not on earth?

Note: These are not rhetorical questions. I am curious how his model of how things behave in the vacuum of space deals with these types of scenarios.
 
  • #58
An object's acceleration is the net result of any and all forces acting on the object, as described by Newton's Second Law.
No such thing as free energy...what you put it in is what you get out...you cannot move the object any further than net force applied which is equal and opposite to both bodies canceling each others acceleration...and why wouldn't it cancel...because the action and the reaction are exactly the same

The reciprocal of 0 force is 0 force. The equal and opposite reaction to 0 would be 0.
 
  • #59
Newtonforce said:
An object's acceleration is the net result of any and all forces acting on the object, as described by Newton's Second Law.
Finally, a true statement!

Newtonforce said:
you cannot move the object any further than net force applied which is equal and opposite to both bodies canceling each others acceleration...and why wouldn't it cancel...because the action and the reaction are exactly the same
Oops... you need to review Newton's 3rd law.

You keep mixing up the equal and opposite forces that objects exert on each other with the net force on each object viewed separately. Those are not the same!
 
  • #60
@Newtonforce
So can a rocket fly in vacuum or not? It is not clear from all these threads what your theory predicts.
 

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