Is it possible to get down by throwing hands upwards?

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In summary, according to Newton's first law, we are unable to move our bodies or change direction in space without an external force acting upon us. However, we can use our arms to throw or swing in order to rotate our position in space. This is due to the principle of conservation of momentum, where the force exerted by our arms creates an equal and opposite reaction in the opposite direction. While we may not be able to move our center of mass, we can still experience rotational motion. This concept is also demonstrated in how cats land on their feet and in the idea of "swimming" in curved space using general relativity. Ultimately, our ability to generate motion depends on the potential energy stored in our bodies, which can be converted
  • #1
Titania
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We are not able to move our bodies, or rather, change direction or accelerate in space without force exerting on it according to Newton's first law.

However, for example, we can throw our right hand in order to move to the left in space.

What if I throw my hands upwards in order to get down ? Is that even possible?

Do correct me if I'm wrong. And sorry for asking this silly question. Thanks in advance :)
 
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  • #2
Your hands are still connected to your body, right? If yes then no you'd still be in the same spot.

Now if you took off your shoes and threw them then you'd get a reaction in the opposite direction.
 
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  • #3
If you flail your arms in space, you WILL move, but only rotationally. Your center of mass will not move but yes, you can change direction
 
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  • #4
Titania said:
What if I throw my hands upwards in order to get down ? Is that even possible?

If you were floating in space and you raised your arms then yes the rest of you would move in the opposite direction. However your centre of mass won't move. When you lower your arms again you will be back in the original starting position.
 
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  • #5
CWatters said:
If you were floating in space and you raised your arms then yes the rest of you would move in the opposite direction. However your centre of mass won't move. When you lower your arms again you will be back in the original starting position.
More to the point, if you SWING your arms, you can rotate your position so you'll be able to see more of the universe while you wait for someone to come rescue you.
 
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  • #6
I got it~ Thanks~
 
  • #7
I don't think you can move down just by throwing your hand up, becuase as a whole you are under no force at all. Maybe you can rotate yourself in the space, but the center of mass of your body cannot move at all.
 
  • #8
phinds said:
More to the point, if you SWING your arms, you can rotate your position so you'll be able to see more of the universe while you wait for someone to come rescue you.

See also how cats turn and land on their feet.
 
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  • #9
This topic reminds me of a Scientific American article from 2009 that explained how you can "swim" in curved, empty space by taking advantage of subtle effects due to general relativity:
http://www.scientificamerican.com/article/surprises-from-general-relativity/
Unfortunately, the whole article isn't available for viewing unless you're subscribed.

To be clear, this is due to GR and in the classical regime you indeed cannot move your center of mass.
 
  • #10
I understand from many reputable authors of popular music that throwing your hands up is, in fact, the standard way to get down.
 
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  • #11
If you are floating weightless, but within your space station... in other words, in a breathable normal atmosphere, you could propel yourself from point A to point B by cupping your hands and paddling - in other words, "Throwing" handfuls of air as you would throw water when swimming. You'd need to force the air backwards pretty hard to move yourself, but I don't see why it wouldn't work.
 
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  • #12
and7barton said:
If you are floating weightless, but within your space station... in other words, in a breathable normal atmosphere, you could propel yourself from point A to point B by cupping your hands and paddling - in other words, "Throwing" handfuls of air as you would throw water when swimming. You'd need to force the air backwards pretty hard to move yourself, but I don't see why it wouldn't work.
Yes, it would work, but that's not what this thread is about.
 
  • #13
DocZaius said:
subtle effects due to general relativity:

And we're back to - almost literally - using GR to solve an inclined plane problem.
 
  • #15
*Cue mid-90s hip-hop references*

Sorry. I had too.:wink:
 
  • #16
and7barton said:
You'd need to force the air backwards pretty hard to move yourself, but I don't see why it wouldn't work.
Probably best to blow and use your mouth / lungs as a rocket engine. The power is better matched to the situation.
 
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  • #17
Actually, you could move by expending work. Not enough space or time here to go into the classical Newtonian physics regarding this. The body does have energy (work) available in the form of ATP, etc. which muscles can use to generate motion and can be directed. With that, motion can be created.
 
  • #18
stevmg said:
Actually, you could move by expending work. Not enough space or time here to go into the classical Newtonian physics regarding this. The body does have energy (work) available in the form of ATP, etc. which muscles can use to generate motion and can be directed. With that, motion can be created.
Not when there's nothing to work ON. You would have to eject mass to change your center of gravity and absent that, it won't move.
 
  • #19
phinds said:
More to the point, if you SWING your arms, you can rotate your position so you'll be able to see more of the universe while you wait for someone to come rescue you.
As demonstrated in SmarterEveryDay 85.
CWatters said:
See also how cats turn and land on their feet.
That too!
 
  • #20
jackwhirl said:
As demonstrated in SmarterEveryDay 85.

That too!

Remember, the body (cats, too) have "potential energy" in the form of ATP and actin which can be expressed as work and create motion. The actual motion is dependent on the living tissue. F = ma. s = (1/2 ) at^2. Depending on t [the time of application of the force] one can back calculate the work expended [from the ATP] to make this motion. Living tissue can generate motion [motion from a point A to point B] because there is potential energy stored up which can be converted to kinetic energy and motion as required.
 
  • #21
stevmg said:
Remember, the body (cats, too) have "potential energy" in the form of ATP and actin which can be expressed as work and create motion. The actual motion is dependent on the living tissue. F = ma. s = (1/2 ) at^2. Depending on t [the time of application of the force] one can back calculate the work expended [from the ATP] to make this motion. Living tissue can generate motion [motion from a point A to point B] because there is potential energy stored up which can be converted to kinetic energy and motion as required.
And how does that happen when there is nothing to push against? You did not answer my previous post. Do you dispute my statement that no amount of work by a free-falling body in space can change the position of its center of mass, absent ejecting some amount of mass?

You keep saying "do work". Do work against WHAT?
 
  • #22
stevmg said:
Remember, the body (cats, too) have "potential energy" in the form of ATP and actin which can be expressed as work and create motion.
But... ATP is a molecule that stores chemical energy, not potential energy. You're right that our bodies can use it to produce motion through our muscles, but as phinds has pointed out, twice now, that motion can't actually move the center of mass without something to push against, in accordance with Newton's first and third laws.
Edit: third, not second, sorry.
 
  • #23
stevmg said:
Living tissue can generate motion [motion from a point A to point B] because there is potential energy stored up which can be converted to kinetic energy and motion as required.
Only if an external force is exerted on the "living tissue".

If you think otherwise, please provide a specific example.
 
  • #24
If you did try blowing air, you are going to have to rotate 180 to breath in or you are defeating the purpose.

Urinating would expel more mass that blowing air.
 
  • #25
itfitmewelltoo said:
If you did try blowing air, you are going to have to rotate 180 to breath in or you are defeating the purpose.

Urinating would expel more mass that blowing air.
Yeah, good point, but in space, if you open your fly bad things might happen to your privates :smile:
 
  • #26
itfitmewelltoo said:
If you did try blowing air, you are going to have to rotate 180 to breath in or you are defeating the purpose.
You don't have to, breathing in takes air from all directions and generates nearly no thrust.
 
  • #27
Doc Al said:
Only if an external force is exerted on the "living tissue".

If you think otherwise, please provide a specific example.

The external force comes from the conversion of potential energy to kinetic energy. Imagine taking a deep breath. Then being placed in space. Then forcibly exhaling and this action-reaction would push the individual the opposite direction of the exhalation.
Similar to a CO2 cartridge in space, at first "immobile," then the creation of a hole in the tip. The action-reaction to the CO2 rushing out would be motion of the cartridge in the opposite direction when before there was no motion of the cartridge. Note than in this case, too, there is NO external force applied to the cartridge other than what subsequently comes from the potential energy that was contained in the cartridge itself.
 
  • #28
stevmg said:
The external force comes from the conversion of potential energy to kinetic energy. Imagine taking a deep breath. Then being placed in space. Then forcibly exhaling and this action-reaction would push the individual the opposite direction of the exhalation.
The external force comes from simply expelling the air! As long as you are willing to "expel" something, you can create an external force. Try doing it without expelling anything. You still have plenty of potential energy stored inside you. Where's the external force now? (Of course, you can always break a piece off and toss it, but that is trivial.)
 
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  • #29
Doc Al said:
The external force comes from simply expelling the air! As long as you are willing to "expel" something, you can create an external force. Try doing it without expelling anything. You still have plenty of potential energy stored inside you. Where's the external force now? (Of course, you can always break a piece off and toss it, but that is trivial.)
This point has been made repeatedly to stevmg, but he ignores it and even failed to answer my direct question about it in post #21
 
  • #30
phinds said:
This point has been made repeatedly to stevmg, but he ignores it and even failed to answer my direct question about it in post #21
Indeed. I eagerly await his response to your direct question. So far, I only see tap dancing around it.
 
  • #31
stevmg said:
Similar to a CO2 cartridge in space, at first "immobile," then the creation of a hole in the tip. The action-reaction to the CO2 rushing out would be motion of the cartridge in the opposite direction when before there was no motion of the cartridge. Note than in this case, too, there is NO external force applied to the cartridge other than what subsequently comes from the potential energy that was contained in the cartridge itself.
If the force from the expelled gas on the cartridge isn't considered to be external, then cartridge and expelled gas are considered one object, whose center of mass doesn't move.
 
  • #32
A.T. said:
If the force from the expelled gas on the cartridge isn't considered to be external, then cartridge and expelled gas are considered one object, whose center of mass doesn't move.
Excellent point.
 
  • #33
athosanian said:
I don't think you can move down just by throwing your hand up, becuase as a whole you are under no force at all. Maybe you can rotate yourself in the space, but the center of mass of your body cannot move at all.
Isn't throwing hands upwards considered as an action? ...I'm confused.
 
  • #34
Titania said:
Isn't throwing hands upwards considered as an action?
What do you mean?
 
  • #35
I'm sorry I sound a bit silly.. But u see, to move your body in space, u will have to exert force or do an action, right? Isn't throwing arms upwards considered as an action? Do correct me.
 
<h2>1. Can throwing your hands upwards really make you go down?</h2><p>No, throwing your hands upwards will not make you go down. This is because the force exerted by your hands is not enough to overcome the force of gravity pulling you towards the ground.</p><h2>2. What is the science behind throwing hands upwards to get down?</h2><p>Throwing your hands upwards is based on the principle of Newton's Third Law of Motion, which states that for every action, there is an equal and opposite reaction. When you throw your hands upwards, your body experiences a force in the opposite direction, but this force is not strong enough to counteract the force of gravity.</p><h2>3. Are there any situations where throwing your hands upwards can make you go down?</h2><p>In certain situations, throwing your hands upwards can help you go down. For example, if you are underwater and need to dive deeper, throwing your hands upwards can create a downward force that helps you go down. However, this is due to the resistance of the water, not the force of your hands alone.</p><h2>4. Is it possible to get down by throwing hands upwards in space?</h2><p>No, it is not possible to get down by throwing your hands upwards in space. In the absence of gravity, there is no force pulling you towards the ground, so throwing your hands upwards will not have any effect on your movement.</p><h2>5. Are there any other ways to get down besides throwing hands upwards?</h2><p>Yes, there are many other ways to get down besides throwing your hands upwards. Some examples include jumping, climbing, using an elevator or stairs, or simply walking down a slope. These methods rely on other forces, such as leg muscles or mechanical devices, to move you downwards.</p>

1. Can throwing your hands upwards really make you go down?

No, throwing your hands upwards will not make you go down. This is because the force exerted by your hands is not enough to overcome the force of gravity pulling you towards the ground.

2. What is the science behind throwing hands upwards to get down?

Throwing your hands upwards is based on the principle of Newton's Third Law of Motion, which states that for every action, there is an equal and opposite reaction. When you throw your hands upwards, your body experiences a force in the opposite direction, but this force is not strong enough to counteract the force of gravity.

3. Are there any situations where throwing your hands upwards can make you go down?

In certain situations, throwing your hands upwards can help you go down. For example, if you are underwater and need to dive deeper, throwing your hands upwards can create a downward force that helps you go down. However, this is due to the resistance of the water, not the force of your hands alone.

4. Is it possible to get down by throwing hands upwards in space?

No, it is not possible to get down by throwing your hands upwards in space. In the absence of gravity, there is no force pulling you towards the ground, so throwing your hands upwards will not have any effect on your movement.

5. Are there any other ways to get down besides throwing hands upwards?

Yes, there are many other ways to get down besides throwing your hands upwards. Some examples include jumping, climbing, using an elevator or stairs, or simply walking down a slope. These methods rely on other forces, such as leg muscles or mechanical devices, to move you downwards.

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