Is it possible to get down by throwing hands upwards?

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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.
 
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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.
 
athosanian said:
I don't think you can move down just by throwing your hand up, because 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.
 
Titania said:
Isn't throwing hands upwards considered as an action?
What do you mean?
 
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.
 
Titania said:
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.
Of course that is an action. The issue you'll run into, if you want to actually travel some distance in space, is that your arms are typically attached to you. If you throw your arms up, that is an action causing an equal and opposite reaction in the rest of your body. But, then your arms reach maximum extension and the force of tension in your arms brings them to a stop, along with the rest of your body which was, briefly, traveling in the opposite direction. Stretching out could let you reach something you couldn't before, but it won't let you go anywhere.
 
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jackwhirl said:
Of course that is an action. The issue you'll run into, if you want to actually travel some distance in space, is that your arms are typically attached to you. If you throw your arms up, that is an action causing an equal and opposite reaction in the rest of your body. But, then your arms reach maximum extension and the force of tension in your arms brings them to a stop, along with the rest of your body which was, briefly, traveling in the opposite direction. Stretching out could let you reach something you couldn't before, but it won't let you go anywhere.
Okay~ Thanks :)
 
Titania said:
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.
Yes, this is correct (I'm assuming you mean "rotate", not move your center of mass). See post #5. This is what everyone in the thread, except stevmg, have said throughout.
 
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