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#1
I've taken two semesters of university physics but I can't seem to comprehend the outcome of this situation.

Assume you're in space, and you throw a punch forward. You stop your fist's momentum as its attached to your body. From here, do you not move, or do you have momentum generated in the direction your fist was travelling?

Assuming that motion occurs, could you place a large piston inside a spaceship that would be accelerated by electromagnets and impact a strong wall inside the ship in order to propel it? This would eliminate the need for fuel entirely as you could use electricity generated from nuclear power or another efficient source.

Am I smart or dumb?
#3
I only know that the dudes at NASA probly would have thought of this first if it's a thing so
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#5
Quote by Bob_Sacamano
I only know that the dudes at NASA probly would have thought of this first if it's a thing so


I think its likely that the forces will just be equal and opposite and nothing would happen.

This Is Not How Space Travel Works You Need Large Amounts Of Speed To Go Anywhere


You could just apply the accelerating force multiple times and it would add cumulatively.
Last edited by Life Is Brutal at Jul 18, 2014,
#6
It would probably be really hard to calculate with precision or something. Also maybe the force needed to move a several ton spaceship might require an improbable sized piston. Also based on the multiple movies and tv shows with space scenes I watched you would spin around and end up upside down if you through a fist
#7
Quote by Life Is Brutal
I've taken two semesters of university physics but I can't seem to comprehend the outcome of this situation.

Assume you're in space

You die from the vacuum and coldness of space.

And I didn't even need 2 semesters of university physics
#9
Forces cancel out, no movement occurs (except the path of motion that they were already on). Since there's an equal and opposite reaction to every action, you'd need to expel (throw) something (like equipment) in one direction, to actually get moving in the other.
#11
Basically, "you" are one object, and you can't exert a force on yourself to get yourself moving. That'd sort of violate energy conservation laws. I think expelling an object from yourself would be analogous to some sort of elastic collision, but it's been a while since my last physics class.
#12
You took two years of physics and they didn't even explain Newton's laws?
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#13
itt ts rekt
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#15
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You took two years of physics and they didn't even explain Newton's laws?


this lol
i don't know why i feel so dry
#18
From what my nerdy side tells me. Yes you would move relative to how hard you punched, because you still retain mass in a zero-G enviroment.

If you wanted to move or stop something in space you need to overcome the inertia of the object to do so.
Often in ones madness resides genius. Thus for a mind seeped in madness, the imagination is limitless.
#19
You know how you can scoot around in your chair by kicking your legs out quickly and then bringing them back in slowly? Just do that in space and get to Mars for free.
Last edited by Jackintehbox at Jul 18, 2014,
#20
I'd rather a warp drive.. or at least some form of lightspeed travell :P
Often in ones madness resides genius. Thus for a mind seeped in madness, the imagination is limitless.
#21
Quote by vocoderboy
could try to use solar wind.


Yeah if you want to take a million years to get the Proxima Centauri
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#22
What if you have a rather heavy ball on an incredibly strong, light rope or something to attach it. Like, a ball that has a mass greater than yours and an infinitely strong fishing line. And you throw the ball. Would you move by the ball pulling you?
#23
Quote by Wisthekiller
What if you have a rather heavy ball on an incredibly strong, light rope or something to attach it. Like, a ball that has a mass greater than yours and an infinitely strong fishing line. And you throw the ball. Would you move by the ball pulling you?


You still need the force necessary to "throw the ball."

This is a terribly inefficient method of travel.

Like, more inefficient then exploding nuclear bombs behind you, riding the shock wave, and accelerating that way.
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#24
Quote by Wisthekiller
What if you have a rather heavy ball on an incredibly strong, light rope or something to attach it. Like, a ball that has a mass greater than yours and an infinitely strong fishing line. And you throw the ball. Would you move by the ball pulling you?

#28
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everything that you've come to expect


#30
Quote by Life Is Brutal
I've taken two semesters of university physics but I can't seem to comprehend the outcome of this situation.

Assume you're in space, and you throw a punch forward. You stop your fist's momentum as its attached to your body. From here, do you not move, or do you have momentum generated in the direction your fist was travelling?

Assuming that motion occurs, could you place a large piston inside a spaceship that would be accelerated by electromagnets and impact a strong wall inside the ship in order to propel it? This would eliminate the need for fuel entirely as you could use electricity generated from nuclear power or another efficient source.

Am I smart or dumb?

Mate, sum of external forces equals dp/dt. Extending your fist or having a piston impact a wall inside a ship, that's an internal force, not external, therefore the center of mass of the system (be it a ship or whatever) does not accelerate.
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#32
Quote by Life Is Brutal
I've taken two semesters of university physics but I can't seem to comprehend the outcome of this situation.

Assume you're in space, and you throw a punch forward. You stop your fist's momentum as its attached to your body. From here, do you not move, or do you have momentum generated in the direction your fist was travelling?

Assuming that motion occurs, could you place a large piston inside a spaceship that would be accelerated by electromagnets and impact a strong wall inside the ship in order to propel it? This would eliminate the need for fuel entirely as you could use electricity generated from nuclear power or another efficient source.

Am I smart or dumb?


Remember you are not in a vacuum. There will be other objects in space, such as planets and suns. You won't be able to go in a straight line because the gravity of these galactic bodies will exert themselves on you.
#35
Well, I think that if you were in space, and you threw a punch forward, and then stopped your first, the main result would be looking like a spaz.
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#36
I would have expected a university course in physics to offer some lessons on the laws of Newton.
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#37
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I would have expected a university course in physics to offer some lessons on the laws of Newton.

Newton's Law is like Newton's love - hard and fast.


Or am I mixing him up with someone else?
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#40
Quote by Dreadnought
You still need the force necessary to "throw the ball."

This is a terribly inefficient method of travel.

Like, more inefficient then exploding nuclear bombs behind you, riding the shock wave, and accelerating that way.



Project Orion FTW!!

Did I ever send you a copy of Pournelle's "A Step Farther Out"? A bit dated but still excellent.

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You would move, you've become a rocket, albeit an inefficient one with exceptionally low Isp.
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Last edited by Arby911 at Jul 19, 2014,
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