# Drag in a Vacuum

russ_watters
Mentor
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.

Doc Al
Mentor
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.

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.

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 thats 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

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

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.

Doc Al
Mentor
for me to apply a force i must be anchored..
Not true.

.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.)

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.

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 wouldnt 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.

Doc Al
Mentor
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!

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 wouldnt 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!

@newtonforce
So can a rocket fly in vacuum or not? It is not clear from all these threads what your theory predicts.

im not talking about here on earth im talking about in a perfect weightless vacuum...

: If there were no gravity, and if the air did not impede the motion of bodies, then any body 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.

what is an impressed force....This force consists in the action only, and remains no longer in the body when the action is over. For a body maintains every new state it acquires by its inertia only. But impressed forces are of different origins, as from percussion, from pressure, from centripetal force.

impressed forces are of different origins, as from percussion, from pressure, from centripetal force.

so me throwing anything in space vacuum would result in the impressed forces from pressure of my arm and equal and opposite force applied to the object and both the object and me will move away from each other and then back toward each other simultaneously.........canceling each others impressed forces so no movement will occur

so me throwing anything in space vacuum would result in the impressed forces from pressure of my arm and equal and opposite force applied to the object and both the object and me will move away from each other and then back toward each other simultaneously.........canceling each others impressed forces so no movement will occur
So what is your response to my scenarios with the ball and the slingshot above?

imstill finding my feet ...but its definatley probable that rockets cannot propell them selves in a space vacuum...by recoil alone...force impressed on rocket chamber are simultaneously moving against and away from rocket chamber... The reciprocal of 0 force is 0 force. The equal and opposite reaction to 0 would be 0.

Doc Al
Mentor
im not talking about here on earth im talking about in a perfect weightless vacuum..
OK.

: If there were no gravity, and if the air did not impede the motion of bodies, then any body 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.
OK.

what is an impressed force....This force consists in the action only, and remains no longer in the body when the action is over.
"impressed" force is just any external force acting on an object. And yes, as soon as you remove it, it no longer acts on the body.

so me throwing anything in space vacuum would result in the impressed forces from pressure of my arm and equal and opposite force applied to the object and both the object and me will move away from each other
You throwing your shoe in space would have you exerting a force on the shoe and the shoe exerting a force on you. You both accelerate and move away from each other. As soon as you break contact you no longer exert forces on each other, you just keep on moving at constant velocity.

and then back toward each other simultaneously.
Why is that?

Doc Al
Mentor
The reciprocal of 0 force is 0 force. The equal and opposite reaction to 0 would be 0.
Why do you keep repeating this strange mantra?

I could just as easily say: The equal and opposite reaction to 10 N of force is 10 N of force. So?

stored energy in the rubber will move the ball as far as the rubber band will recoil ...what has been impressed onto the ball that the ball did not impress back to the rubberband
The reciprocal of 0 force is 0 force. The equal and opposite reaction to 0 would be 0.

Doc Al
Mentor
but its definatley probable that rockets cannot propell them selves in a space vacuum
Seriously?

.force impressed on rocket chamber are simultaneously moving against and away from rocket chamber...

stored energy in the rubber will move the ball as far as the rubber band will recoil ...what has been impressed onto the ball that the ball did not impress back to the rubberband
The reciprocal of 0 force is 0 force. The equal and opposite reaction to 0 would be 0.
So you're pulling the rubber band back, the pebble along with it. You let go of the rubber band and it propels itself and the pebble forward. The rubber band eventually stretches forward to a point where it cannot go further forward. This is what happens on earth and in space.

But now you say that things start to differ at this point. You're saying that now the pebble will stick to the rubber band in space and go no further than the rubber band while on earth the pebble will detach itself form the rubber band and keep moving forward. Correct?

The reason I am doing this is to illustrate (hopefully to you!) that there are some seriously bizarre consequences that come from your model.

how can motion be achieved by a balanced equation...there has to be a differential between the interior and the exterior...

Again and again, you still don't understand Newton's 3rd law. There is nothing more to say.

SammyS
Doc Al
Mentor